feat: setup websockify

This change makes it possible
to connect the client over WebSocket.
Running `websocat wss://example.org/imap`
connects to the IMAP
and running `websocat wss://example.org/smtp`
connects to SMTP (submission service, not port 25).

Connecting from a web client will still need a CORS policy
for clients not running on the same domain,
but for non-web clients this is already usable.

.github/workflows/ci-no-dns.yaml

@@ -20,9 +20,11 @@ concurrency:
 jobs:
   no-dns:
     name: LXC deploy and test
-    uses: chatmail/cmlxc/.github/workflows/lxc-test.yml@v0.14.6
+    permissions:
+      contents: read
+    uses: chatmail/cmlxc/.github/workflows/lxc-test.yml@main
     with:
-      cmlxc_version: v0.14.6
+      cmlxc_version: main
       cmlxc_commands: |
         cmlxc init 
         # single cmdeploy relay test

.github/workflows/ci.yaml

@@ -29,7 +29,7 @@ jobs:
           ref: ${{ github.event.pull_request.head.sha }}
           persist-credentials: false
       - name: download filtermail
-        run: curl -L https://github.com/chatmail/filtermail/releases/download/v0.6.6/filtermail-x86_64 -o /usr/local/bin/filtermail && chmod +x /usr/local/bin/filtermail
+        run: curl -L https://github.com/chatmail/filtermail/releases/download/v0.7.4/filtermail-x86_64 -o /usr/local/bin/filtermail && chmod +x /usr/local/bin/filtermail
       - name: run chatmaild tests 
         working-directory: chatmaild
         run: pipx run tox
@@ -57,9 +57,11 @@ jobs:
 
   lxc-test:
     name: LXC deploy and test
-    uses: chatmail/cmlxc/.github/workflows/lxc-test.yml@v0.14.6
+    permissions:
+      contents: read
+    uses: chatmail/cmlxc/.github/workflows/lxc-test.yml@main
     with:
-      cmlxc_version: v0.14.6
+      cmlxc_version: main
       cmlxc_commands: |
         cmlxc init 
         # single cmdeploy relay test

.github/workflows/docker-dispatch.yaml

@@ -9,6 +9,7 @@ name: Trigger Docker build
 on:
   push:
     branches: [main]
+    tags: ['[0-9]+.[0-9]+.[0-9]+']
   workflow_dispatch:
 
 permissions: {}

.github/workflows/docs-preview.yaml

@@ -51,7 +51,7 @@ jobs:
           mkdir -p "$HOME/.ssh"
           echo "${{ secrets.CHATMAIL_STAGING_SSHKEY }}" > "$HOME/.ssh/key"
           chmod 600 "$HOME/.ssh/key"
-          rsync -rILvh -e "ssh -i $HOME/.ssh/key -o StrictHostKeyChecking=no" $GITHUB_WORKSPACE/doc/build/ "${{ secrets.USERNAME }}@chatmail.at:/var/www/html/staging.chatmail.at/doc/relay/${STEPS_PREPARE_OUTPUTS_PRID}/"
+          rsync -rILvh -e "ssh -i $HOME/.ssh/key -o StrictHostKeyChecking=no" $GITHUB_WORKSPACE/doc/build/ "${{ secrets.USERNAME }}@chatmail.at:${STEPS_PREPARE_OUTPUTS_PRID}/"
         env:
           STEPS_PREPARE_OUTPUTS_PRID: ${{ steps.prepare.outputs.prid }}
 

CHANGELOG.md

@@ -1,4 +1,46 @@
-# Changelog for chatmail deployment 
+# Changelog for chatmail deployment
+
+## [1.11.0] - 2026-05-15
+
+### Breaking Changes
+
+- [**breaking**] Drop passthrough_sender and passthrough_recipients chatmail.ini options to eliminate one more source of unencrypted messages
+
+### Features
+
+- Use filtermail for delivery to remote MTAs
+- Expose metadata "maxsmtprecipients" value
+- Support setup without domain, with only an IPv4 address (#963)
+- *(doc/docker)* Introduce docker images in documentation
+- DKIM-sign bounce messages (mainly "user does not exist")
+- *(config)* Load default values from Config(), not chatmail.ini.f (#853)
+- Make turn_socket_path configurable, and cleanup tests and turnserver code.
+- Warn about any unused chatmail.ini parameter at the end of "cmdeploy run"
+
+### Bug Fixes
+
+- Make www tests work with editable instead of just plain installs
+- Use path with no leading slash for mxdeliv
+- Increase filtermail-transport concurrency limit
+- Fix #972 by increasing file descriptors for filtermail
+- *(mtail)* Correct boot ordering and deploy restart logic
+- *(cmdeploy)* Stop and disable unbound-resolvconf
+- *(nginx)* Properly redirect www to mail_domain
+- *(dns)* Query correct NS if MNAME server is hidden (#954)
+- Legacy token metadata storage used list type, but if no new setmetadata happened, the user would not be notified at all.
+- *(logging)* Log all http requests to syslog
+
+### Documentation
+
+- Document how to upgrade to new version (#965)
+
+### Other
+
+- *(deps)* Upgrade to filtermail v0.6.4
+
+### Refactor
+
+- Introduce automated change-tracking across deployers
 
 ## 1.10.0 2026-04-30
 

README.md

@@ -1,19 +1,24 @@
 
 # Chatmail relays for end-to-end encrypted email
 
-Chatmail relay servers are interoperable Mail Transport Agents (MTAs) designed for: 
+Chatmail relay servers are interoperable Mail Transport Agents (MTAs) designed for:
 
 -  **Zero State:** no private data or metadata collected, messages are auto-deleted, low disk usage
 
 -  **Instant/Realtime:** sub-second message delivery, realtime P2P
    streaming, privacy-preserving Push Notifications for Apple, Google, and Huawei;
 
--  **Security Enforcement**: only strict TLS, DKIM and OpenPGP with minimized metadata accepted
+-  **Security Enforcement**: Only connections with strict TLS are accepted;
+   all messages must be correctly signed with DKIM and OpenPGP-encrypted with minimized metadata.
+   There are experimental exceptions for no-DNS relays,
+   which are allowed use self-signed TLS certificates
+   and which do not need to DKIM-sign their messages.
+   Unencrypted messages are allowed in neither case.
 
 -  **Reliable Federation and Decentralization:** No spam or IP reputation checks, federating
    depends on established IETF standards and protocols.
 
-This repository contains everything needed to setup a ready-to-use chatmail relay on an ssh-reachable host. 
+This repository contains everything needed to setup a ready-to-use chatmail relay on an ssh-reachable host.
 For getting started and more information please refer to the web version of this repositories' documentation at
 
 [https://chatmail.at/doc/relay](https://chatmail.at/doc/relay)

chatmaild/pyproject.toml

@@ -8,9 +8,9 @@ version = "0.3"
 dependencies = [
   "iniconfig",
   "filelock",
+  "psutil",
   "requests",
-  "crypt-r >= 3.13.1 ; python_version >= '3.11'",
-  "domain-validator",
+  "crypt-r >= 3.13.1 ; python_version >= '3.13'",
 ]
 
 [tool.setuptools]

chatmaild/src/chatmaild/config.py

@@ -2,7 +2,6 @@ import ipaddress
 from pathlib import Path
 
 import iniconfig
-from domain_validator import DomainValidator
 
 from chatmaild.user import User
 
@@ -16,7 +15,8 @@ def read_config(inipath):
 class Config:
     def __init__(self, inipath, params):
         self._inipath = inipath
-        raw_domain = params["mail_domain"]
+        params = dict(params)
+        raw_domain = params.pop("mail_domain")
         self.mail_domain_bare = raw_domain
 
         if is_valid_ipv4(raw_domain):
@@ -24,65 +24,73 @@ class Config:
             self.mail_domain = f"[{raw_domain}]"
             self.postfix_myhostname = ipaddress.IPv4Address(raw_domain).reverse_pointer
         else:
-            DomainValidator().validate_domain_re(raw_domain)
             self.ipv4_relay = None
             self.mail_domain = raw_domain
             self.postfix_myhostname = raw_domain
 
-        self.max_user_send_per_minute = int(params.get("max_user_send_per_minute", 60))
-        self.max_user_send_burst_size = int(params.get("max_user_send_burst_size", 10))
-        self.max_mailbox_size = params.get("max_mailbox_size", "500M")
-        self.max_message_size = int(params.get("max_message_size", 31457280))
-        self.delete_mails_after = params.get("delete_mails_after", "20")
-        self.delete_large_after = params.get("delete_large_after", "7")
+        self.max_user_send_per_minute = int(params.pop("max_user_send_per_minute", 60))
+        self.max_user_send_burst_size = int(params.pop("max_user_send_burst_size", 10))
+        self.max_mailbox_size = params.pop("max_mailbox_size", "500M")
+        self.max_message_size = int(params.pop("max_message_size", 31457280))
+        self.delete_mails_after = params.pop("delete_mails_after", "20")
+        self.delete_large_after = params.pop("delete_large_after", "7")
         self.delete_inactive_users_after = int(
-            params.get("delete_inactive_users_after", 90)
+            params.pop("delete_inactive_users_after", 90)
         )
-        self.username_min_length = int(params.get("username_min_length", 9))
-        self.username_max_length = int(params.get("username_max_length", 9))
-        self.password_min_length = int(params.get("password_min_length", 9))
-        self.passthrough_senders = params.get("passthrough_senders", "").split()
-        self.passthrough_recipients = params.get("passthrough_recipients", "").split()
-        self.www_folder = params.get("www_folder", "")
-        self.filtermail_smtp_port = int(params.get("filtermail_smtp_port", "10080"))
+        self.username_min_length = int(params.pop("username_min_length", 9))
+        self.username_max_length = int(params.pop("username_max_length", 9))
+        self.password_min_length = int(params.pop("password_min_length", 9))
+        self.www_folder = params.pop("www_folder", "")
+        self.filtermail_smtp_port = int(params.pop("filtermail_smtp_port", "10080"))
         self.filtermail_smtp_port_incoming = int(
-            params.get("filtermail_smtp_port_incoming", "10081")
+            params.pop("filtermail_smtp_port_incoming", "10081")
         )
         self.filtermail_http_port_incoming = int(
-            params.get("filtermail_http_port_incoming", "10082")
+            params.pop("filtermail_http_port_incoming", "10082")
         )
         self.filtermail_lmtp_port_transport = int(
-            params.get("filtermail_lmtp_port_transport", "10083")
+            params.pop("filtermail_lmtp_port_transport", "10083")
         )
-        self.postfix_reinject_port = int(params.get("postfix_reinject_port", "10025"))
+        self.postfix_reinject_port = int(params.pop("postfix_reinject_port", "10025"))
         self.postfix_reinject_port_incoming = int(
-            params.get("postfix_reinject_port_incoming", "10026")
+            params.pop("postfix_reinject_port_incoming", "10026")
         )
-        self.mtail_address = params.get("mtail_address")
-        self.disable_ipv6 = params.get("disable_ipv6", "false").lower() == "true"
-        self.acme_email = params.get("acme_email", "")
-        self.imap_rawlog = params.get("imap_rawlog", "false").lower() == "true"
-        self.imap_compress = params.get("imap_compress", "false").lower() == "true"
-        self.turn_socket_path = params.get(
+        self.mtail_address = params.pop("mtail_address", None)
+        self.disable_ipv6 = params.pop("disable_ipv6", "false").lower() == "true"
+        self.acme_email = params.pop("acme_email", "")
+        self.imap_rawlog = params.pop("imap_rawlog", "false").lower() == "true"
+        self.imap_compress = params.pop("imap_compress", "false").lower() == "true"
+        self.turn_socket_path = params.pop(
             "turn_socket_path", "/run/chatmail-turn/turn.socket"
         )
-        if "iroh_relay" not in params:
+        iroh_relay = params.pop("iroh_relay", None)
+        if iroh_relay is None:
             self.iroh_relay = "https://" + raw_domain
             self.enable_iroh_relay = True
         else:
-            self.iroh_relay = params["iroh_relay"].strip()
+            self.iroh_relay = iroh_relay.strip()
             self.enable_iroh_relay = False
-        self.privacy_postal = params.get("privacy_postal")
-        self.privacy_mail = params.get("privacy_mail")
-        self.privacy_pdo = params.get("privacy_pdo")
-        self.privacy_supervisor = params.get("privacy_supervisor")
+        self.privacy_postal = params.pop("privacy_postal", None)
+        self.privacy_mail = params.pop("privacy_mail", None)
+        self.privacy_pdo = params.pop("privacy_pdo", None)
+        self.privacy_supervisor = params.pop("privacy_supervisor", None)
+
+        self.max_load_1m = float(params.pop("max_load_1m", 5))
+        self.min_available_memory_mb = parse_size_mb(
+            params.pop("min_available_memory", "200M")
+        )
+        self.min_free_disk_space_mb = parse_size_mb(
+            params.pop("min_free_disk_space", "1G")
+        )
+        self.max_imap_connections = int(params.pop("max_imap_connections", 10000))
+        self.max_smtp_connections = int(params.pop("max_smtp_connections", 1000))
 
         # TLS certificate management.
         # If tls_external_cert_and_key is set, use externally managed certs.
         # Otherwise derived from the domain name:
         # - Domains starting with "_" use self-signed certificates
         # - All other domains use ACME.
-        external = params.get("tls_external_cert_and_key", "").strip()
+        external = params.pop("tls_external_cert_and_key", "").strip()
 
         if external:
             parts = external.split()
@@ -103,11 +111,12 @@ class Config:
             self.tls_key_path = f"/var/lib/acme/live/{raw_domain}/privkey"
 
         # deprecated option
-        mbdir = params.get("mailboxes_dir", f"/home/vmail/mail/{raw_domain}")
+        mbdir = params.pop("mailboxes_dir", f"/home/vmail/mail/{raw_domain}")
         self.mailboxes_dir = Path(mbdir.strip())
 
         # old unused option (except for first migration from sqlite to maildir store)
-        self.passdb_path = Path(params.get("passdb_path", "/home/vmail/passdb.sqlite"))
+        self.passdb_path = Path(params.pop("passdb_path", "/home/vmail/passdb.sqlite"))
+        self._unused_keys = list(params)
 
     @property
     def max_mailbox_size_mb(self):

chatmaild/src/chatmaild/doveauth.py

@@ -14,6 +14,7 @@ except ImportError:
 from .config import Config, read_config
 from .dictproxy import DictProxy
 from .migrate_db import migrate_from_db_to_maildir
+from .syslimits import has_sufficient_resources
 
 NOCREATE_FILE = "/etc/chatmail-nocreate"
 VALID_LOCALPART_RE = re.compile(r"^[a-z0-9._-]+$")
@@ -147,6 +148,8 @@ class AuthDictProxy(DictProxy):
             return userdata
         if not is_allowed_to_create(self.config, addr, cleartext_password):
             return
+        if not has_sufficient_resources(self.config):
+            return
 
         lock = filelock.FileLock(str(user.password_path) + ".lock", timeout=5)
         with lock:

chatmaild/src/chatmaild/expire.py

@@ -168,6 +168,16 @@ class Expiry:
         if mbox.last_login and mbox.last_login < cutoff_without_login:
             self.remove_mailbox(mbox.basedir)
             return
+        elif mbox.last_login is None:
+            try:
+                if not self.dry:
+                    os.rmdir(mbox.basedir)
+                    self.del_mboxes += 1
+            except OSError:
+                print_info(
+                    f"Skipped deleting {mbox.basedir}, doesn't have last_login but isn't empty"
+                )
+            return
 
         mboxname = os.path.basename(mbox.basedir)
         if self.verbose:

chatmaild/src/chatmaild/ini/chatmail.ini.f

@@ -42,12 +42,32 @@ mail_domain = {mail_domain}
 # minimum length a password must have
 #password_min_length = 9
 
-# list of chatmail addresses which can send outbound un-encrypted mail
-#passthrough_senders =
+#
+# System resource limits
+#
 
-# list of e-mail recipients for which to accept outbound un-encrypted mails
-# (space-separated, item may start with "@" to whitelist whole recipient domains)
-#passthrough_recipients =
+# The following three limits refuse creation of new addresses
+# while existing addresses keep working.
+# Rejections are logged by the doveauth service.
+
+# Maximum 1-minute load average, as reported by "uptime";
+# it counts processes waiting for disk I/O as well as for CPU.
+#max_load_1m = 5
+
+# Minimum memory available without swapping.
+#min_available_memory = 200M
+
+# Minimum free disk space on the file system holding the mailboxes.
+#min_free_disk_space = 1G
+
+# Maximum number of concurrent IMAP connections
+# (the Dovecot imap process limit).
+#max_imap_connections = 10000
+
+# Maximum number of concurrent SMTP connections
+# on each of the submission and smtps ports (the Postfix process limit).
+# A single client IP may use up to a fifth of this.
+#max_smtp_connections = 1000
 
 # Use externally managed TLS certificates instead of built-in acmetool.
 # Paths refer to files on the deployment server (not the build machine).

chatmaild/src/chatmaild/syslimits.py

@@ -0,0 +1,32 @@
+"""Detect whether the system is at its limits."""
+
+import logging
+
+import psutil
+
+MB = 1024 * 1024
+
+
+def read_value(getter):
+    try:
+        return getter()
+    except Exception as e:
+        logging.warning("ignoring unreadable system limit: %s", e)
+        return None
+
+
+def has_sufficient_resources(config):
+    """Return False if load, memory or disk exceeds a configured limit."""
+    load = read_value(lambda: psutil.getloadavg()[0])
+    mem = read_value(lambda: psutil.virtual_memory().available // MB)
+    disk = read_value(lambda: psutil.disk_usage(str(config.mailboxes_dir)).free // MB)
+    if load is not None and load > config.max_load_1m:
+        msg = f"load avg {load:.2f} > {config.max_load_1m:.2f}"
+    elif mem is not None and mem < config.min_available_memory_mb:
+        msg = f"available memory {mem}MB < {config.min_available_memory_mb}MB"
+    elif disk is not None and disk < config.min_free_disk_space_mb:
+        msg = f"free disk {disk}MB < {config.min_free_disk_space_mb}MB"
+    else:
+        return True
+    logging.warning("registration rejected: %s", msg)
+    return False

chatmaild/src/chatmaild/tests/plugin.py

@@ -20,6 +20,10 @@ def make_config(tmp_path):
         basedir.mkdir(parents=True, exist_ok=True)
         overrides = settings.copy() if settings else {}
         overrides["mailboxes_dir"] = str(basedir)
+        # permissive resource limits so tests never depend on host load/memory/disk
+        overrides.setdefault("max_load_1m", "99999")
+        overrides.setdefault("min_available_memory", "0")
+        overrides.setdefault("min_free_disk_space", "0")
         write_initial_config(inipath, mail_domain, overrides=overrides)
         return read_config(inipath)
 

chatmaild/src/chatmaild/tests/test_config.py

@@ -45,8 +45,14 @@ def test_read_config_basic_using_defaults(tmp_path, maildomain):
     assert example_config.username_min_length == 9
     assert example_config.username_max_length == 9
     assert example_config.password_min_length == 9
-    assert example_config.passthrough_recipients == []
-    assert example_config.passthrough_senders == []
+    assert example_config.max_imap_connections == 10000
+    assert example_config.max_smtp_connections == 1000
+    assert example_config._unused_keys == []
+
+
+def test_config_unused_keys(make_config):
+    config = make_config("chat.example.org", {"passthrough_senders": "x@y.org"})
+    assert config._unused_keys == ["passthrough_senders"]
 
 
 def test_config_userstate_paths(make_config, tmp_path):

chatmaild/src/chatmaild/tests/test_doveauth.py

@@ -202,3 +202,17 @@ def test_50_concurrent_lookups_different_accounts(gencreds, dictproxy):
         res = results.get()
         if res is not None:
             pytest.fail(f"concurrent lookup failed\n{res}")
+
+
+def test_insufficient_resources_block_creation_not_existing_logins(
+    dictproxy, gencreds, monkeypatch
+):
+    addr, password = gencreds()
+    assert dictproxy.lookup_passdb(addr, password)
+
+    monkeypatch.setattr(
+        chatmaild.doveauth, "has_sufficient_resources", lambda config: False
+    )
+    newaddr, newpassword = gencreds()
+    assert not dictproxy.lookup_passdb(newaddr, newpassword)
+    assert dictproxy.lookup_passdb(addr, password)

chatmaild/src/chatmaild/tests/test_expire.py

@@ -1,6 +1,7 @@
 import itertools
 import os
 import random
+import shutil
 import time
 from datetime import datetime
 from fnmatch import fnmatch
@@ -9,6 +10,7 @@ from pathlib import Path
 import pytest
 
 from chatmaild.expire import (
+    Expiry,
     FileEntry,
     MailboxStat,
     expire_to_target,
@@ -104,6 +106,32 @@ def test_stats_mailbox(mbox1):
     assert mbox3.last_login is None
 
 
+def test_mbox_without_password(mbox1, example_config, capsys):
+    password = Path(mbox1.basedir).joinpath("password")
+    os.remove(password)
+    mbox_rescan = MailboxStat(mbox1.basedir)
+    assert mbox_rescan.last_login is None
+
+    exp = Expiry(
+        example_config, dry=False, now=datetime.now().timestamp(), verbose=False
+    )
+    exp.process_mailbox_stat(mbox_rescan)
+    out, err = capsys.readouterr()
+    assert "doesn't have last_login but isn't empty" in err
+    assert os.path.isdir(mbox_rescan.basedir)
+
+    for entry in os.scandir(mbox_rescan.basedir):
+        if os.path.isdir(entry):
+            shutil.rmtree(entry)
+        else:
+            os.remove(entry)
+
+    exp.process_mailbox_stat(mbox_rescan)
+    out, err = capsys.readouterr()
+    assert "doesn't have last_login but isn't empty" not in err
+    assert not os.path.isdir(mbox_rescan.basedir)
+
+
 def test_report_no_mailboxes(example_config):
     args = (str(example_config._inipath),)
     report_main(args)

chatmaild/src/chatmaild/tests/test_syslimits.py

@@ -0,0 +1,45 @@
+import shutil
+
+import psutil
+
+from chatmaild.syslimits import has_sufficient_resources
+
+PERMISSIVE = {
+    "max_load_1m": "99999",
+    "min_available_memory": "0",
+    "min_free_disk_space": "0",
+}
+
+
+def test_rejects_constrained_system(make_config, caplog):
+    assert has_sufficient_resources(make_config("chat.example.org", PERMISSIVE))
+    for settings in (
+        {"max_load_1m": "-1.0"},
+        {"min_available_memory": "99999999G"},
+        {"min_free_disk_space": "99999999G"},
+    ):
+        config = make_config("chat.example.org", PERMISSIVE | settings)
+        caplog.clear()
+        assert not has_sufficient_resources(config), settings
+        assert "registration rejected" in caplog.text
+
+
+def test_unreadable_disk_does_not_reject(make_config, caplog):
+    config = make_config(
+        "chat.example.org", PERMISSIVE | {"min_free_disk_space": "99999999G"}
+    )
+    shutil.rmtree(config.mailboxes_dir)
+    assert has_sufficient_resources(config)
+    assert "ignoring" in caplog.text
+
+
+def test_one_unreadable_value_keeps_other_checks(make_config, monkeypatch, caplog):
+    def raise_error(*args):
+        raise psutil.Error("dud")
+
+    monkeypatch.setattr(psutil, "getloadavg", raise_error)
+    config = make_config(
+        "chat.example.org", PERMISSIVE | {"min_free_disk_space": "99999999G"}
+    )
+    assert not has_sufficient_resources(config)
+    assert "ignoring" in caplog.text

cmdeploy/src/cmdeploy/acmetool/response-file.yaml.j2

@@ -1,2 +1,2 @@
 "acme-enter-email": "{{ email }}"
-"acme-agreement:https://letsencrypt.org/documents/LE-SA-v1.6-August-18-2025.pdf": true
+"acme-agreement:https://letsencrypt.org/documents/LE-SA-v1.8-July-06-2026.pdf": true

cmdeploy/src/cmdeploy/basedeploy.py

@@ -166,7 +166,7 @@ class Deployer:
             return self.put_template(src, dest, **kwargs)
         return self.put_file(src, dest)
 
-    def put_file(self, src, dest, mode="644"):
+    def put_file(self, src, dest, mode="644", **kwargs):
         if isinstance(src, str):
             src = get_resource(src)
         res = files.put(
@@ -176,6 +176,7 @@ class Deployer:
             user="root",
             group="root",
             mode=mode,
+            **kwargs,
         )
 
         return self._update_restart_signals(dest, res)

cmdeploy/src/cmdeploy/cmdeploy.py

@@ -84,6 +84,15 @@ def run_cmd_options(parser):
     add_ssh_host_option(parser)
 
 
+def _warn_unused_settings(unused_keys, out):
+    if unused_keys:
+        names = ", ".join(unused_keys)
+        out.red(
+            f"WARNING: chatmail.ini contains settings that have no effect: {names}\n"
+            "Please remove them from chatmail.ini."
+        )
+
+
 def run_cmd(args, out):
     """Deploy chatmail services on the remote server."""
 
@@ -125,6 +134,7 @@ def run_cmd(args, out):
             out.green("Deploy completed.")
         else:
             out.green("Deploy completed, call `cmdeploy dns` next.")
+        _warn_unused_settings(args.config._unused_keys, out)
         return 0
     except subprocess.CalledProcessError:
         out.red("Deploy failed")

cmdeploy/src/cmdeploy/deployers.py

@@ -32,6 +32,7 @@ from .external.deployer import ExternalTlsDeployer
 from .filtermail.deployer import FiltermailDeployer
 from .mtail.deployer import MtailDeployer
 from .nginx.deployer import NginxDeployer
+from .websockify.deployer import WebsockifyDeployer
 from .opendkim.deployer import OpendkimDeployer
 from .postfix.deployer import PostfixDeployer
 from .selfsigned.deployer import SelfSignedTlsDeployer
@@ -138,9 +139,22 @@ class UnboundDeployer(Deployer):
         # On an IPv4-only system, if unbound is started but not configured,
         # it causes subsequent steps to fail to resolve hosts.
         with blocked_service_startup():
+            # dns-root-data is an optional package
+            # that contains /usr/share/dns/root.key
+            #
+            # This file is copied into /var/lib/unbound/root.key
+            # at the start of "unbound" systemd unit
+            # by /usr/libexec/unbound-helper shell script
+            # from the "unbound" package as of version 1.17.1-2+deb12u4
+            #
+            # The same /var/lib/unbound/root.key can be retrieved directly
+            # following the procedure from
+            # <https://www.rfc-editor.org/info/rfc7958/#section-3.1>
+            # with "unbound-anchor -a /var/lib/unbound/root.key"
+            # We don't install and use "unbound-anchor".
             apt.packages(
                 name="Install unbound",
-                packages=["unbound", "unbound-anchor", "dnsutils"],
+                packages=["unbound", "dns-root-data", "dnsutils"],
             )
 
     def configure(self):
@@ -164,23 +178,16 @@ class UnboundDeployer(Deployer):
         self.put_file(
             src=BytesIO(b"nameserver 127.0.0.1\nnameserver 9.9.9.9\n"),
             dest="/etc/resolv.conf",
+            force=True,
         )
-        server.shell(
-            name="Generate root keys for validating DNSSEC",
-            commands=[
-                "unbound-anchor -a /var/lib/unbound/root.key || true",
-            ],
+        self.ensure_directory(
+            path="/etc/unbound/unbound.conf.d",
+        )
+        self.put_template(
+            "unbound/unbound.conf.j2",
+            "/etc/unbound/unbound.conf.d/chatmail.conf",
+            disable_ipv6=self.config.disable_ipv6,
         )
-        if self.config.disable_ipv6:
-            self.ensure_directory(
-                path="/etc/unbound/unbound.conf.d",
-            )
-            self.put_template(
-                "unbound/unbound.conf.j2",
-                "/etc/unbound/unbound.conf.d/chatmail.conf",
-            )
-        else:
-            self.remove_file("/etc/unbound/unbound.conf.d/chatmail.conf")
 
     def activate(self):
         server.shell(
@@ -247,6 +254,13 @@ class LegacyRemoveDeployer(Deployer):
     def install(self):
         apt.packages(name="Remove rspamd", packages="rspamd", present=False)
 
+        # unbound-anchor was used to download /var/lib/unbound/root.key
+        # It is replaced by dns-root-data which contains /usr/share/dns/root.key.
+        # unbound systemd unit copies /usr/share/dns/root.key
+        # into /var/lib/unbound/root.key automatically on start
+        # as long as /usr/share/dns/root.key is present.
+        apt.packages(name="Remove unbound-anchor", packages="unbound-anchor", present=False)
+
         # remove historic expunge script
         # which is now implemented through a systemd timer (chatmail-expire)
         self.remove_file("/etc/cron.d/expunge")
@@ -357,6 +371,8 @@ class ChatmailVenvDeployer(Deployer):
     def __init__(self, config):
         self.config = config
         self.units = (
+            # doveauth must restart when chatmaild/ini file changes
+            "doveauth",
             "chatmail-metadata",
             "lastlogin",
             "chatmail-expire",
@@ -514,6 +530,8 @@ def deploy_chatmail(config_path: Path, disable_mail: bool, website_only: bool) -
             (["master", "smtpd"], config.postfix_reinject_port_incoming),
             ("filtermail", config.filtermail_smtp_port),
             ("filtermail", config.filtermail_smtp_port_incoming),
+            ("filtermail", config.filtermail_http_port_incoming),
+            ("filtermail", config.filtermail_lmtp_port_transport),
         ]
         for service, port in port_services:
             print(f"Checking if port {port} is available for {service}...")
@@ -548,6 +566,7 @@ def deploy_chatmail(config_path: Path, disable_mail: bool, website_only: bool) -
         PostfixDeployer(config, disable_mail),
         FcgiwrapDeployer(),
         NginxDeployer(config),
+        WebsockifyDeployer(config),
         MtailDeployer(config.mtail_address),
         GithashDeployer(),
     ]

cmdeploy/src/cmdeploy/dovecot/deployer.py

@@ -34,7 +34,7 @@ class DovecotDeployer(Deployer):
     def __init__(self, config, disable_mail):
         self.config = config
         self.disable_mail = disable_mail
-        self.units = ["doveauth"]
+        self.units = []
 
     def install(self):
         arch = host.get_fact(Arch)

cmdeploy/src/cmdeploy/dovecot/dovecot.conf.j2

@@ -37,11 +37,15 @@ default_client_limit = 20000
 # the following warning will be logged:
 #   Warning: service(imap): process_limit (1024) reached, client connections are being dropped
 service imap {
-  process_limit = 50000
+  process_limit = {{ config.max_imap_connections }}
 }
 
-mail_server_admin = mailto:root@{{ config.mail_domain }}
-mail_server_comment = Chatmail server
+{% if config.privacy_mail %}
+# Advertised to clients as IMAP METADATA /shared/admin (RFC 5464).
+# The privacy_mail contact from chatmail.ini is used because it is
+# the only address set by an operator.
+mail_server_admin = mailto:{{ config.privacy_mail }}
+{% endif %}
 
 # `zlib` enables compressing messages stored in the maildir.
 # See

cmdeploy/src/cmdeploy/filtermail/deployer.py

@@ -20,10 +20,10 @@ class FiltermailDeployer(Deployer):
             return
 
         arch = host.get_fact(facts.server.Arch)
-        url = f"https://github.com/chatmail/filtermail/releases/download/v0.6.6/filtermail-{arch}"
+        url = f"https://github.com/chatmail/filtermail/releases/download/v0.7.4/filtermail-{arch}"
         sha256sum = {
-            "x86_64": "05c7e7ac244606c2eeb275f2d282ffdbc2403e0169f1cdd3110ffcebdb994a92",
-            "aarch64": "8cf8bbda4d907beca547b365cc7e6753532a74b1712492d0d2f3d2d8a553fb3d",
+            "x86_64": "484cb8dff083134aefba9fce4a6b7ef4784a0f0e28e5108ecf8bb9e58a44fd2c",
+            "aarch64": "66aa0ca2ca9add7a12d92883d76f8786384092adfde24a3d3a1d0b1f30d23a9e",
         }[arch]
         self.download_executable(url, self.bin_path, sha256sum)
 

cmdeploy/src/cmdeploy/filtermail/filtermail-transport.service.j2

@@ -6,6 +6,7 @@ ExecStart={{ bin_path }} {{ config_path }} transport
 Restart=always
 RestartSec=30
 User=vmail
+LimitNOFILE=524288
 
 [Install]
 WantedBy=multi-user.target

cmdeploy/src/cmdeploy/mtail/delivered_mail.mtail

@@ -28,6 +28,13 @@ counter created_nonci_accounts
   }
 }
 
+# doveauth refusing new addresses because a chatmail.ini
+# system resource limit is exceeded.
+counter rejected_registrations
+/registration rejected: / {
+  rejected_registrations++
+}
+
 counter postfix_timeouts
 /timeout after DATA/ {
   postfix_timeouts++
@@ -73,6 +80,11 @@ counter incoming_unencrypted_mail_count
   filtered_incoming_mail_count++
 }
 
+counter incoming_mailer_daemon_mail_count
+/Incoming: Filtering mailer-daemon message from/ {
+  incoming_mailer_daemon_mail_count++
+  filtered_incoming_mail_count++
+}
 
 counter rejected_unencrypted_mail_count
 /Rejected unencrypted mail/ {

cmdeploy/src/cmdeploy/nginx/nginx.conf.j2

@@ -128,7 +128,10 @@ http {
                         proxy_set_header Connection "upgrade";
                 }
 
-		location /relay/probe {
+		# Endpoints Iroh uses for net_report probes and that clients
+		# probe to tell whether this relay works. Both paths are served
+		# by iroh-relay 0.35 and by the 1.0 line.
+		location /ping {
                         proxy_pass http://127.0.0.1:3340;
                         proxy_http_version 1.1;
 		}
@@ -137,6 +140,20 @@ http {
                         proxy_pass http://127.0.0.1:3340;
                         proxy_http_version 1.1;
 		}
+
+		location /imap {
+			proxy_pass http://127.0.0.1:8143;
+			proxy_http_version 1.1;
+			proxy_set_header Upgrade $http_upgrade;
+			proxy_set_header Connection "upgrade";
+		}
+
+		location /smtp {
+			proxy_pass http://127.0.0.1:8587;
+			proxy_http_version 1.1;
+			proxy_set_header Upgrade $http_upgrade;
+			proxy_set_header Connection "upgrade";
+		}
 	}
 
 	# Redirect www. to non-www

cmdeploy/src/cmdeploy/postfix/lmtp_header_cleanup

@@ -1,5 +1,3 @@
-/^From:/            DUNNO
-/^Message-Id:/      DUNNO
-/^Chat-Is-Post-Message:/      DUNNO
-/^Content-Type:/    DUNNO
-/.*/                IGNORE
+/^DKIM-Signature:/            IGNORE
+/^Authentication-Results:/            IGNORE
+/^Received:/            IGNORE

cmdeploy/src/cmdeploy/postfix/main.cf.j2

@@ -53,7 +53,8 @@ smtpd_tls_exclude_ciphers = aNULL, RC4, MD5, DES
 # See <https://www.postfix.org/FORWARD_SECRECY_README.html#server_fs>.
 tls_preempt_cipherlist = yes
 
-smtpd_relay_restrictions = permit_mynetworks permit_sasl_authenticated defer_unauth_destination
+# Reject by default, override per smtpd in master.cf
+smtpd_relay_restrictions = reject
 myhostname = {{ config.postfix_myhostname }}
 alias_maps = hash:/etc/aliases
 alias_database = hash:/etc/aliases
@@ -84,6 +85,14 @@ inet_protocols = all
 
 lmtp_header_checks = regexp:/etc/postfix/lmtp_header_cleanup
 
+# Do not apply header checks to MIME headers
+# and other headers that are actually part of the message body.
+# Reference:
+# <https://www.postfix.org/postconf.5.html#disable_mime_input_processing>
+# <https://www.postfix.org/header_checks.5.html>
+# <https://stump.io/blog/2020/11/29/a-little-gotcha-with-postfixs-header_checks/>
+disable_mime_input_processing = yes
+
 mua_client_restrictions = permit_sasl_authenticated, reject
 mua_sender_restrictions = reject_sender_login_mismatch, permit_sasl_authenticated, reject
 mua_helo_restrictions = permit_mynetworks, reject_invalid_helo_hostname, reject_non_fqdn_helo_hostname, permit
@@ -101,9 +110,24 @@ smtpd_peername_lookup = no
 # so instead this is handled in filtermail.
 # We use LMTP instead SMTP so we can communicate per-recipient errors back to postfix.
 default_transport = lmtp-filtermail:inet:[127.0.0.1]:{{ config.filtermail_lmtp_port_transport }}
+
+# All deliveries over lmtp-filtermail are treated
+# as having the same destination [127.0.0.1],
+# so it is not possible to limit per-destination concurrency here,
+# it is a job for filtermail-transport.
+# Total number of parallel deliveries is limited
+# by "maxproc" column in /etc/postfix/master.cf for lmtp-filtermail.
+# Settings below are to prevent Postfix queue manager
+# from limiting the number of LMTP connections to filtermail-transport.
+# Read <https://www.postfix.org/TUNING_README.html#rope> and
+# <https://www.postfix.org/SCHEDULER_README.html> for the details
+# of the Postfix algorithm that we effectively disable here.
 lmtp-filtermail_initial_destination_concurrency=10000
 lmtp-filtermail_destination_concurrency_limit=10000
 
+# Do not try to deliver messages for more than 2 days.
+maximal_queue_lifetime = 2d
+
 {% if not config.ipv4_relay %}
 # DKIM-sign locally generated mail (bounces, DSNs).
 # These bypass smtpd, so they need explicit milter configuration.

cmdeploy/src/cmdeploy/postfix/master.cf.j2

@@ -17,7 +17,8 @@ smtp      inet  n       -       y       -       -       smtpd
   -o smtpd_tls_security_level=encrypt
   -o smtpd_tls_mandatory_protocols=>=TLSv1.2
   -o smtpd_proxy_filter=127.0.0.1:{{ config.filtermail_smtp_port_incoming }}
-submission inet n       -       y       -       5000    smtpd
+  -o smtpd_relay_restrictions=reject_unauth_destination
+submission inet n       -       y       -       {{ config.max_smtp_connections }}    smtpd
   -o syslog_name=postfix/submission
   -o smtpd_tls_security_level=encrypt
   -o smtpd_tls_mandatory_protocols=>=TLSv1.3
@@ -31,9 +32,9 @@ submission inet n       -       y       -       5000    smtpd
   -o smtpd_sender_restrictions=$mua_sender_restrictions
   -o smtpd_recipient_restrictions=
   -o smtpd_relay_restrictions=permit_sasl_authenticated,reject
-  -o smtpd_client_connection_count_limit=1000
+  -o smtpd_client_connection_count_limit={{ config.max_smtp_connections // 5 }}
   -o smtpd_proxy_filter=127.0.0.1:{{ config.filtermail_smtp_port }}
-smtps     inet  n       -       y       -       5000    smtpd
+smtps     inet  n       -       y       -       {{ config.max_smtp_connections }}    smtpd
   -o syslog_name=postfix/smtps
   -o smtpd_tls_wrappermode=yes
   -o smtpd_tls_security_level=encrypt
@@ -47,7 +48,7 @@ smtps     inet  n       -       y       -       5000    smtpd
   -o smtpd_sender_restrictions=$mua_sender_restrictions
   -o smtpd_recipient_restrictions=
   -o smtpd_relay_restrictions=permit_sasl_authenticated,reject
-  -o smtpd_client_connection_count_limit=1000
+  -o smtpd_client_connection_count_limit={{ config.max_smtp_connections // 5 }}
   -o smtpd_proxy_filter=127.0.0.1:{{ config.filtermail_smtp_port }}
 #628       inet  n       -       y       -       -       qmqpd
 pickup    unix  n       -       y       60      1       pickup
@@ -75,18 +76,19 @@ lmtp      unix  -       -       y       -       -       lmtp
 anvil     unix  -       -       y       -       1       anvil
 scache    unix  -       -       y       -       1       scache
 postlog   unix-dgram n  -       n       -       1       postlogd
-filter    unix -        n       n       -       -       lmtp
 # Local SMTP server for reinjecting outgoing filtered mail.
 127.0.0.1:{{ config.postfix_reinject_port }} inet  n       -       n       -       100      smtpd
   -o syslog_name=postfix/reinject
   -o milter_macro_daemon_name=ORIGINATING
   -o cleanup_service_name=authclean
+  -o smtpd_relay_restrictions=permit_mynetworks,reject
 {% if not config.ipv4_relay %}  -o smtpd_milters=unix:opendkim/opendkim.sock
 {% endif %}
 
 # Local SMTP server for reinjecting incoming filtered mail 
 127.0.0.1:{{ config.postfix_reinject_port_incoming }} inet  n       -       n       -       100      smtpd
   -o syslog_name=postfix/reinject_incoming
+  -o smtpd_relay_restrictions=reject_unauth_destination
 
 # Cleanup `Received` headers for authenticated mail
 # to avoid leaking client IP.
@@ -102,7 +104,15 @@ filter    unix -        n       n       -       -       lmtp
 authclean unix  n       -       -       -       0       cleanup
   -o header_checks=regexp:/etc/postfix/submission_header_cleanup
 
-lmtp-filtermail unix  -       -       y       -       10000       lmtp
+# Reducing `maxproc` here may result in a head of line blocking
+# when there are many messages sent to unreachable destinations
+# at the same time.
+# LMTP clients here talk to filtermail-transport.
+# LMTP has no pipelining,
+# so while filtermail-transport tries to deliver the message,
+# possibly waiting for a long connection timeout
+# or talking to a slow server, LMTP client cannot be reused.
+lmtp-filtermail unix  -       -       y       -       500       lmtp
   -o syslog_name=postfix/lmtp-filtermail
   -o lmtp_header_checks=
   -o lmtp_tls_security_level=none

cmdeploy/src/cmdeploy/tests/online/test_1_basic.py

@@ -232,6 +232,26 @@ def try_n_times(n, f):
     return f()
 
 
+def test_rewrite_subject(cmsetup, maildata):
+    """Test that subject gets replaced with [...]."""
+    user1, user2 = cmsetup.gen_users(2)
+
+    sent_msg = maildata(
+        "encrypted.eml",
+        from_addr=user1.addr,
+        to_addr=user2.addr,
+        subject="Unencrypted subject",
+    ).as_string()
+    user1.smtp.sendmail(from_addr=user1.addr, to_addrs=[user2.addr], msg=sent_msg)
+
+    # The message may need some time to get delivered by postfix.
+    messages = try_n_times(5, user2.imap.fetch_all_messages)
+    assert len(messages) == 1
+    rcvd_msg = messages[0]
+    assert "Subject: [...]" not in sent_msg
+    assert "Subject: [...]" in rcvd_msg
+    assert "Subject: Unencrypted subject" in sent_msg
+    assert "Subject: Unencrypted subject" not in rcvd_msg
 
 
 def test_exceed_rate_limit(cmsetup, gencreds, maildata, chatmail_config):

cmdeploy/src/cmdeploy/tests/plugin.py

@@ -10,13 +10,11 @@ from pathlib import Path
 
 import pytest
 from chatmaild.config import is_valid_ipv4, read_config
-from domain_validator import DomainValidator
 
 
 def format_mail_domain(raw_domain: str) -> str:
     if is_valid_ipv4(raw_domain):
         return f"[{raw_domain}]"
-    DomainValidator().validate_domain_re(raw_domain)
     return raw_domain
 
 
@@ -349,9 +347,9 @@ class ChatmailACFactory:
                 qr = (
                     f"dclogin:{addr}"
                     f"?p={password}&v=1"
-                    f"&ih={domain}&ip=993"
-                    f"&sh={domain}&sp=465"
-                    f"&ic=3&ss=default"
+                    f"&ih={domain}&ip=993&is=ssl"
+                    f"&sh={domain}&sp=465&ss=ssl"
+                    f"&ic=3"
                 )
                 future = account.add_transport_from_qr.future(qr)
             else:
@@ -362,7 +360,7 @@ class ChatmailACFactory:
 
             # ensure messages stay in INBOX so that they can be
             # concurrently fetched via extra IMAP connections during tests
-            account.set_config("delete_server_after", "10")
+            account.set_config("bcc_self", "1")
             accounts.append(account)
 
         for future in futures:

cmdeploy/src/cmdeploy/unbound/unbound.conf.j2

@@ -1,4 +1,7 @@
-# Managed by cmdeploy: disable IPv6 in unbound.
+# Managed by cmdeploy
 server:
+{% if disable_ipv6 %}
   interface: 127.0.0.1
   do-ip6: no
+{% endif %}
+  cache-max-negative-ttl: 0

cmdeploy/src/cmdeploy/websockify/deployer.py

@@ -0,0 +1,19 @@
+from pyinfra.operations import apt, server
+
+from cmdeploy.basedeploy import Deployer
+
+
+class WebsockifyDeployer(Deployer):
+    def __init__(self, config):
+        self.config = config
+
+    def install(self):
+        apt.packages(name="Install websockify", packages=["websockify"])
+
+    def configure(self):
+        self.ensure_systemd_unit("websockify/websockify-imap.service")
+        self.ensure_systemd_unit("websockify/websockify-submission.service")
+
+    def activate(self):
+        self.ensure_service("websockify-imap.service")
+        self.ensure_service("websockify-submission.service")

cmdeploy/src/cmdeploy/websockify/websockify-imap.service

@@ -0,0 +1,12 @@
+[Unit]
+Description=WebSocket proxy for IMAP
+After=network.target
+
+[Service]
+Type=simple
+Restart=always
+ExecStart=/usr/bin/websockify 127.0.0.1:8143 localhost:143
+DynamicUser=true
+
+[Install]
+WantedBy=multi-user.target

cmdeploy/src/cmdeploy/websockify/websockify-submission.service

@@ -0,0 +1,12 @@
+[Unit]
+Description=WebSocket proxy for SMTP
+After=network.target
+
+[Service]
+Type=simple
+Restart=always
+ExecStart=/usr/bin/websockify 127.0.0.1:8587 localhost:587
+DynamicUser=true
+
+[Install]
+WantedBy=multi-user.target

doc/source/faq.rst

@@ -60,6 +60,7 @@ and run the following commands:
    ::
 
        git pull origin main --rebase --autostash
+       scripts/initenv.sh
        scripts/cmdeploy run
 
 If you don't want the latest development version,

doc/source/getting_started.rst

@@ -199,6 +199,93 @@ creating addresses, login with ssh to the deployment machine and run:
 Chatmail address creation will be denied while this file is present.
 
 
+.. _system-limits:
+
+Configurable System Limits
+--------------------------
+
+Limits for auto-rejecting address creation
+..........................................
+
+A relay refuses creation of new addresses
+when the machine runs low on resources,
+but existing addresses keep working.
+
+Three ``chatmail.ini`` settings control this,
+shown here with their defaults::
+
+    max_load_1m = 5
+    min_available_memory = 200M
+    min_free_disk_space = 1G
+
+- ``max_load_1m`` is the maximum 1-minute load average,
+  as reported by ``uptime``;
+  it counts processes waiting for disk I/O as well as for CPU.
+  It is deliberately not scaled by the number of CPUs
+  because I/O rather than CPU is what typically limits a relay.
+
+- ``min_available_memory`` is the minimum memory available without swapping.
+
+- ``min_free_disk_space`` is the minimum free disk space
+  on the file system holding the mailboxes.
+
+The defaults suit the small machine described in
+`Minimal requirements and prerequisites`_.
+
+.. note::
+
+   If you run a bigger machine,
+   raise ``max_load_1m`` after watching ``uptime`` under typical load.
+
+Rejections are logged by the ``doveauth`` service,
+so you can check whether a limit is set too tightly::
+
+    journalctl -u doveauth --grep 'registration rejected'
+
+If ``mtail_address`` is set, rejections are also counted
+in the ``rejected_registrations`` metric.
+
+
+Overall IMAP and SMTP connection limits
+.......................................
+
+Two further settings bound how many connections
+the relay accepts at all, again shown with their defaults::
+
+    max_imap_connections = 10000
+    max_smtp_connections = 1000
+
+``max_imap_connections`` becomes the Dovecot imap process limit,
+and ``max_smtp_connections`` the Postfix process limit
+on each of the submission and smtps ports.
+A single client IP may use up to a fifth of ``max_smtp_connections``.
+Each connection costs memory,
+so these limits defend the relay against running out of RAM.
+
+Unless ``imap_compress`` is enabled,
+an IMAP connection that is idle for ``imap_hibernate_timeout``
+is handed over to the ``imap-hibernate`` process
+and does not count towards ``max_imap_connections``,
+which is why a relay can serve far more IMAP clients
+than this setting suggests.
+
+If you run a large relay with 10k or 100k's of addresses,
+check current connection counts before upgrading
+and set the limits accordingly.
+
+To see how close a running relay is to these two limits,
+copy ``scripts/check-connections.sh`` from the relay repository
+onto the relay and run it there::
+
+    imap             5  ports 143,993   (max_imap_connections)
+                     5  dovecot sessions, 0 of them in an active imap process
+    submission       0  ports 465,587   (max_smtp_connections per port)
+    incoming         0  port 25         (from other relays, no chatmail.ini limit)
+
+It counts established sockets with ``ss``
+and cross-checks the IMAP number against ``doveadm who``.
+
+
 Running a relay with self-signed certificates
 ----------------------------------------------
 

doc/source/overview.rst

@@ -156,6 +156,7 @@ Chatmail relay dependency diagram
         postfix --- |10083|filtermail-transport;
         filtermail-outgoing --- |10025 reinject|postfix;
         filtermail-incoming --- |10026 reinject|postfix;
+        postfix --- |milter opendkim.sock|OpenDKIM
         dovecot --- |doveauth.socket|doveauth;
         dovecot --- |message delivery|maildir["maildir
         /home/vmail/.../user"];
@@ -179,26 +180,51 @@ Chatmail relay dependency diagram
         style nginx-right fill:#f66;
         style postfix fill:#f66;
         style dovecot fill:#f66;
+        style OpenDKIM fill:#f66;
         style notification-proxy fill:#f66;
 
-Message between users on the same relay
----------------------------------------
+Accepting and delivering mail
+-----------------------------
 
 .. mermaid::
-    :caption: This diagram shows the path a non-federated message takes.
+    :caption: This diagram shows all the paths a message can take.
 
-    graph LR;
-        sender --> |465|smtps/smtpd;
-        sender --> |587|submission/smtpd;
-        smtps/smtpd --> |10080|filtermail;
-        submission/smtpd --> |10080|filtermail;
-        filtermail --> |10025|smtpd_reinject;
-        smtpd_reinject --> cleanup;
-        cleanup --> qmgr;
-        qmgr --> smtpd_accepts_message;
-        qmgr --> |lmtp|dovecot;
-        dovecot --> recipient;
-        dovecot --> sender's_other_devices;
+    flowchart LR
+        subgraph chatmail relay
+            subgraph postfix
+                qmgr .-> lmtp-filtermail["lmtp/lmtp-filtermail (default_transport)"]
+                qmgr .-> lmtp["lmtp (local_transport)"]
+                lmtp --> cleanup["cleanup (lmtp_header_cleanup)"]
+                bounce
+                smtpd-submission["smtpd/submission"]
+                smtpd-smtps["smtpd/smtps"]
+                smtpd-reinject-outgoing["smtpd/reinject-outgoing"] --> authclean["cleanup/authclean (submission_header_cleanup)"]
+                authclean --> qmgr
+                smtpd-smtp["smtpd/smtp"]
+                smtpd-reinject-incoming["smtpd/reinject-incoming"] --> qmgr
+            end
+            lmtp-filtermail --LMTP inet:10083--> filtermail-transport
+            cleanup --LMTP unix:private/dovecot-lmtp --> dovecot
+            dovecot --> maildir
+            smtpd-submission --SMTP inet:10080--> filtermail-outgoing
+            smtpd-smtps --SMTP inet:10080--> filtermail-outgoing
+            filtermail-outgoing --SMTP inet:10025--> smtpd-reinject-outgoing
+            open-dkim["OpenDKIM (signing only)"] <--milter unix:opendkim/opendkim.sock--> smtpd-reinject-outgoing
+            bounce <--milter unix:opendkim/opendkim.sock--> open-dkim
+            bounce --> qmgr
+            nginx
+            smtpd-smtp -.SMTP inet:10081.-> filtermail-incoming
+            nginx -.HTTP inet:10082.-> filtermail-incoming
+            filtermail-incoming --SMTP inet:10026--> smtpd-reinject-incoming
+        end
+        filtermail-transport -.SMTP inet:25.-> mta1[Remote relay]
+        filtermail-transport -.HTTPS /mxdeliv.-> mta1
+        client[Client] -.SMTP inet:587.-> smtpd-submission
+        client -.SMTP inet:465.-> smtpd-smtps
+        client -.SMTP inet:443.-> nginx
+        nginx -.SMTP inet:465.-> smtpd-smtps
+        mta2[Remote relay] -.SMTP inet:25.-> smtpd-smtp
+        mta2 -.HTTPS /mxdeliv.-> nginx
 
 Operational details of a chatmail relay
 ----------------------------------------

scripts/check-connections.sh

@@ -0,0 +1,26 @@
+#!/bin/bash
+#
+# Show current IMAP and SMTP connections on a chatmail relay,
+# to compare against the max_imap_connections and max_smtp_connections
+# settings in chatmail.ini.  Run this on the relay itself.
+set -e
+
+# Count established TCP connections whose local port is one of the arguments.
+established() {
+    filter=$(printf 'sport = :%s or ' "$@")
+    ss -Htn state established "( ${filter% or } )" | wc -l
+}
+
+# doveadm prints a header line and then one line per logged-in user,
+# with that user's number of connections in the second column.
+sessions=$(doveadm who | awk 'NR > 1 { n += $2 } END { print n + 0 }')
+
+# Unless imap_compress is enabled, connections idle for
+# imap_hibernate_timeout are handed over to the imap-hibernate
+# process, so they cost no imap process while idle.
+active=$(pgrep -x imap | wc -l)
+
+printf 'imap        %6d  ports 143,993   (max_imap_connections)\n' "$(established 143 993)"
+printf '            %6d  dovecot sessions, %d of them in an active imap process\n' "$sessions" "$active"
+printf 'submission  %6d  ports 465,587   (max_smtp_connections per port)\n' "$(established 465 587)"
+printf 'incoming    %6d  port 25         (from other relays, no chatmail.ini limit)\n' "$(established 25)"