fix: DNS check timeout with IPv6-broken authoritative NS

Add IPv4 fallback for authoritative NS queries in query_dns().
When dig @ns returns no useful answer (e.g. IPv6 transport to
the NS times out), retry with -4 to force IPv4. Also limits
timeout and tries (+timeout=10 +tries=2) to avoid hanging.

Fixes #851

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

@@ -1,35 +0,0 @@
-name: No-DNS
-
-on:
-  # Triggers when a PR is merged into main or a direct push occurs
-  push:
-    branches: [ "main" ]
-    
-  # Triggers for any PR (and its subsequent commits) targeting the main branch
-  pull_request:
-    branches: [ "main" ]
-
-# Newest push wins: Prevents multiple runs from clashing and wasting runner efforts
-concurrency:
-  group: ${{ github.workflow }}-${{ github.event.pull_request.number || github.ref }}
-  cancel-in-progress: true
-
-
-jobs:
-  no-dns:
-    name: LXC deploy and test
-    uses: chatmail/cmlxc/.github/workflows/lxc-test.yml@d39fe34c39cee6d760c3479325e8dc82b66a8928
-    with:
-      cmlxc_commands: |
-        cmlxc init 
-        # single cmdeploy relay test
-        cmlxc -v deploy-cmdeploy --source ./repo --ipv4-only --no-dns cm0
-        cmlxc -v test-cmdeploy --no-dns cm0
-
-        # cross cmdeploy relay test
-        cmlxc -v deploy-cmdeploy --source ./repo cm1
-        cmlxc -v test-cmdeploy --no-dns cm0 cm1
-
-        # cross cmdeploy/madmail relay tests
-        cmlxc -v deploy-madmail mad0
-        cmlxc -v test-cmdeploy --no-dns cm0 mad0

.github/workflows/ci.yaml

@@ -1,4 +1,4 @@
-name: CI
+name: Run unit-tests and container-based deploy+test verification
 
 on:
   # Triggers when a PR is merged into main or a direct push occurs
@@ -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/v0.6.4/filtermail-x86_64 -o /usr/local/bin/filtermail && chmod +x /usr/local/bin/filtermail
+        run: curl -L https://github.com/chatmail/filtermail/releases/download/v0.6.1/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
@@ -57,7 +57,7 @@ jobs:
 
   lxc-test:
     name: LXC deploy and test
-    uses: chatmail/cmlxc/.github/workflows/lxc-test.yml@d39fe34c39cee6d760c3479325e8dc82b66a8928
+    uses: chatmail/cmlxc/.github/workflows/lxc-test.yml@v0.10.0
     with:
       cmlxc_commands: |
         cmlxc init 

chatmaild/pyproject.toml

@@ -10,7 +10,6 @@ dependencies = [
   "filelock",
   "requests",
   "crypt-r >= 3.13.1 ; python_version >= '3.11'",
-  "domain-validator",
 ]
 
 [tool.setuptools]

chatmaild/src/chatmaild/config.py

@@ -1,8 +1,6 @@
-import ipaddress
 from pathlib import Path
 
 import iniconfig
-from domain_validator import DomainValidator
 
 from chatmaild.user import User
 
@@ -21,19 +19,7 @@ def read_config(inipath):
 class Config:
     def __init__(self, inipath, params):
         self._inipath = inipath
-        raw_domain = params["mail_domain"]
-        self.mail_domain_bare = raw_domain
-
-        if is_valid_ipv4(raw_domain):
-            self.ipv4_relay = raw_domain
-            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.mail_domain = params["mail_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["max_mailbox_size"]
@@ -54,9 +40,6 @@ class Config:
         self.filtermail_http_port_incoming = int(
             params.get("filtermail_http_port_incoming", "10082")
         )
-        self.filtermail_lmtp_port_transport = int(
-            params.get("filtermail_lmtp_port_transport", "10083")
-        )
         self.postfix_reinject_port = int(params.get("postfix_reinject_port", "10025"))
         self.postfix_reinject_port_incoming = int(
             params.get("postfix_reinject_port_incoming", "10026")
@@ -67,7 +50,7 @@ class Config:
         self.imap_rawlog = params.get("imap_rawlog", "false").lower() == "true"
         self.imap_compress = params.get("imap_compress", "false").lower() == "true"
         if "iroh_relay" not in params:
-            self.iroh_relay = "https://" + raw_domain
+            self.iroh_relay = "https://" + params["mail_domain"]
             self.enable_iroh_relay = True
         else:
             self.iroh_relay = params["iroh_relay"].strip()
@@ -93,17 +76,17 @@ class Config:
                 )
             self.tls_cert_mode = "external"
             self.tls_cert_path, self.tls_key_path = parts
-        elif raw_domain.startswith("_") or self.ipv4_relay:
+        elif self.mail_domain.startswith("_"):
             self.tls_cert_mode = "self"
             self.tls_cert_path = "/etc/ssl/certs/mailserver.pem"
             self.tls_key_path = "/etc/ssl/private/mailserver.key"
         else:
             self.tls_cert_mode = "acme"
-            self.tls_cert_path = f"/var/lib/acme/live/{raw_domain}/fullchain"
-            self.tls_key_path = f"/var/lib/acme/live/{raw_domain}/privkey"
+            self.tls_cert_path = f"/var/lib/acme/live/{self.mail_domain}/fullchain"
+            self.tls_key_path = f"/var/lib/acme/live/{self.mail_domain}/privkey"
 
         # deprecated option
-        mbdir = params.get("mailboxes_dir", f"/home/vmail/mail/{raw_domain}")
+        mbdir = params.get("mailboxes_dir", f"/home/vmail/mail/{self.mail_domain}")
         self.mailboxes_dir = Path(mbdir.strip())
 
         # old unused option (except for first migration from sqlite to maildir store)
@@ -189,27 +172,3 @@ def get_default_config_content(mail_domain, **overrides):
                 lines.append(line)
         content = "\n".join(lines)
     return content
-
-
-def is_valid_ipv4(address: str) -> bool:
-    """Check if a mail_domain is an IPv4 address."""
-    try:
-        ipaddress.IPv4Address(address)
-        return True
-    except ValueError:
-        return False
-
-
-
-def format_arpa_address(address: str) -> str:
-    if is_valid_ipv4(address):
-        return ipaddress.IPv4Address(address).reverse_pointer
-    DomainValidator().validate_domain_re(address)
-    return address
-
-
-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

chatmaild/src/chatmaild/newemail.py

@@ -2,6 +2,7 @@
 
 """CGI script for creating new accounts."""
 
+import ipaddress
 import json
 import secrets
 import string
@@ -14,6 +15,16 @@ ALPHANUMERIC = string.ascii_lowercase + string.digits
 ALPHANUMERIC_PUNCT = string.ascii_letters + string.digits + string.punctuation
 
 
+def wrap_ip(host):
+    if host.startswith("[") and host.endswith("]"):
+        return host
+    try:
+        ipaddress.ip_address(host)
+        return f"[{host}]"
+    except ValueError:
+        return host
+
+
 def create_newemail_dict(config: Config):
     user = "".join(
         secrets.choice(ALPHANUMERIC) for _ in range(config.username_max_length)
@@ -22,22 +33,16 @@ def create_newemail_dict(config: Config):
         secrets.choice(ALPHANUMERIC_PUNCT)
         for _ in range(config.password_min_length + 3)
     )
-    return dict(email=f"{user}@{config.mail_domain}", password=f"{password}")
+    return dict(email=f"{user}@{wrap_ip(config.mail_domain)}", password=f"{password}")
 
 
-def create_dclogin_url(config, email, password):
+def create_dclogin_url(email, password):
     """Build a dclogin: URL with credentials and self-signed cert acceptance.
 
     Uses ic=3 (AcceptInvalidCertificates) so chatmail clients
     can connect to servers with self-signed TLS certificates.
     """
-    if config.ipv4_relay:
-        imap_host = "&ih=" + config.ipv4_relay
-        smtp_host = "&sh=" + config.ipv4_relay
-    else:
-        imap_host = ""
-        smtp_host = ""
-    return f"dclogin:{quote(email, safe='@[]')}?p={quote(password, safe='')}&v=1{imap_host}{smtp_host}&ic=3"
+    return f"dclogin:{quote(email, safe='@')}?p={quote(password, safe='')}&v=1&ic=3"
 
 
 def print_new_account():
@@ -46,9 +51,7 @@ def print_new_account():
 
     result = dict(email=creds["email"], password=creds["password"])
     if config.tls_cert_mode == "self":
-        result["dclogin_url"] = create_dclogin_url(
-            config, creds["email"], creds["password"]
-        )
+        result["dclogin_url"] = create_dclogin_url(creds["email"], creds["password"])
 
     print("Content-Type: application/json")
     print("")

chatmaild/src/chatmaild/tests/plugin.py

@@ -31,11 +31,6 @@ def example_config(make_config):
     return make_config("chat.example.org")
 
 
-@pytest.fixture
-def ipv4_config(make_config):
-    return make_config("1.3.3.7")
-
-
 @pytest.fixture
 def maildomain(example_config):
     return example_config.mail_domain

chatmaild/src/chatmaild/tests/test_config.py

@@ -1,14 +1,6 @@
-from contextlib import nullcontext as does_not_raise
-
 import pytest
 
-from chatmaild.config import (
-    format_arpa_address,
-    format_mail_domain,
-    is_valid_ipv4,
-    parse_size_mb,
-    read_config,
-)
+from chatmaild.config import parse_size_mb, read_config
 
 
 def test_read_config_basic(example_config):
@@ -21,12 +13,6 @@ def test_read_config_basic(example_config):
     example_config = read_config(inipath)
     assert example_config.max_user_send_per_minute == 37
     assert example_config.mail_domain == "chat.example.org"
-    assert example_config.ipv4_relay is None
-
-
-def test_read_config_ipv4(ipv4_config):
-    assert ipv4_config.ipv4_relay == "1.3.3.7"
-    assert ipv4_config.mail_domain == "[1.3.3.7]"
 
 
 def test_read_config_basic_using_defaults(tmp_path, maildomain):
@@ -149,45 +135,3 @@ def test_max_mailbox_size_mb(make_config):
     config = make_config("chat.example.org")
     assert config.max_mailbox_size == "500M"
     assert config.max_mailbox_size_mb == 500
-
-
-@pytest.mark.parametrize(
-    ["input", "result"],
-    [
-        ("example.org", False),
-        ("1.3.3.7", True),
-        ("fe::1", False),
-        ("ad.1e.dag.adf", False),
-        ("12394142", False),
-    ],
-)
-def test_is_valid_ipv4(input, result):
-    assert result == is_valid_ipv4(input)
-
-
-@pytest.mark.parametrize(
-    ["input", "result", "exception"],
-    [
-        ("example.org", "example.org", does_not_raise()),
-        ("1.3.3.7", "7.3.3.1.in-addr.arpa", does_not_raise()),
-        ("fe::1", None, pytest.raises(ValueError)),
-        ("12394142", None, pytest.raises(ValueError)),
-    ],
-)
-def test_format_arpa_address(input, result, exception):
-    with exception:
-        assert result == format_arpa_address(input)
-
-
-@pytest.mark.parametrize(
-    ["input", "result", "exception"],
-    [
-        ("example.org", "example.org", does_not_raise()),
-        ("1.3.3.7", "[1.3.3.7]", does_not_raise()),
-        ("fe::1", None, pytest.raises(ValueError)),
-        ("12394142", None, pytest.raises(ValueError)),
-    ],
-)
-def test_format_mail_domain(input, result, exception):
-    with exception:
-        assert result == format_mail_domain(input)

chatmaild/src/chatmaild/tests/test_newmail.py

@@ -19,35 +19,24 @@ def test_create_newemail_dict(example_config):
     assert ac1["password"] != ac2["password"]
 
 
-def test_create_newemail_dict_ip(ipv4_config):
-    ac = create_newemail_dict(ipv4_config)
-    assert ac["email"].endswith("@[1.3.3.7]")
+def test_create_newemail_dict_ip(make_config):
+    config = make_config("1.2.3.4")
+    ac = create_newemail_dict(config)
+    assert ac["email"].endswith("@[1.2.3.4]")
 
 
-def test_create_dclogin_url(example_config):
-    addr = "user@example.org"
-    password = "p@ss w+rd"
-    url = create_dclogin_url(example_config, addr, password)
+def test_create_dclogin_url():
+    url = create_dclogin_url("user@example.org", "p@ss w+rd")
     assert url.startswith("dclogin:")
     assert "v=1" in url
     assert "ic=3" in url
 
-    assert addr in url
+    assert "user@example.org" in url
     # password special chars must be encoded
     assert "p%40ss" in url
     assert "w%2Brd" in url
 
 
-def test_create_dclogin_url_ipv4(ipv4_config):
-    addr = "user@[1.3.3.7]"
-    password = "p@ss w+rd"
-    url = create_dclogin_url(ipv4_config, addr, password)
-    assert url.startswith("dclogin:")
-    assert "v=1" in url
-    assert "ic=3" in url
-    assert addr in url
-
-
 def test_print_new_account(capsys, monkeypatch, maildomain, tmpdir, example_config):
     monkeypatch.setattr(chatmaild.newemail, "CONFIG_PATH", str(example_config._inipath))
     print_new_account()

cmdeploy/src/cmdeploy/cmdeploy.py

@@ -87,12 +87,10 @@ def run_cmd_options(parser):
 def run_cmd(args, out):
     """Deploy chatmail services on the remote server."""
 
-    ssh_host = args.ssh_host if args.ssh_host else args.config.mail_domain_bare
+    ssh_host = args.ssh_host if args.ssh_host else args.config.mail_domain
     sshexec = get_sshexec(ssh_host)
     require_iroh = args.config.enable_iroh_relay
     strict_tls = args.config.tls_cert_mode == "acme"
-    if args.config.ipv4_relay:
-        args.dns_check_disabled = True
     if not args.dns_check_disabled:
         remote_data = dns.get_initial_remote_data(sshexec, args.config.mail_domain)
         if not dns.check_initial_remote_data(remote_data, strict_tls=strict_tls, print=out.red):
@@ -121,8 +119,6 @@ def run_cmd(args, out):
         elif not args.dns_check_disabled and strict_tls and not remote_data["acme_account_url"]:
             out.red("Deploy completed but letsencrypt not configured")
             out.red("Run 'cmdeploy run' again")
-        elif args.config.ipv4_relay:
-            out.green("Deploy completed.")
         else:
             out.green("Deploy completed, call `cmdeploy dns` next.")
         return 0
@@ -144,10 +140,6 @@ def dns_cmd_options(parser):
 
 def dns_cmd(args, out):
     """Check DNS entries and optionally generate dns zone file."""
-    if args.config.ipv4_relay:
-        ipv4 = args.config.ipv4_relay
-        print(f"[WARNING] {ipv4} is not a domain, skipping DNS checks.")
-        return 0
     ssh_host = args.ssh_host if args.ssh_host else args.config.mail_domain
     sshexec = get_sshexec(ssh_host, verbose=args.verbose)
     tls_cert_mode = args.config.tls_cert_mode
@@ -185,7 +177,7 @@ def status_cmd_options(parser):
 def status_cmd(args, out):
     """Display status for online chatmail instance."""
 
-    ssh_host = args.ssh_host if args.ssh_host else args.config.mail_domain_bare
+    ssh_host = args.ssh_host if args.ssh_host else args.config.mail_domain
     sshexec = get_sshexec(ssh_host, verbose=args.verbose)
 
     out.green(f"chatmail domain: {args.config.mail_domain}")

cmdeploy/src/cmdeploy/deployers.py

@@ -468,7 +468,7 @@ class ChatmailVenvDeployer(Deployer):
 
     def configure(self):
         _configure_remote_venv_with_chatmaild(self.config)
-        configure_remote_units(self.config.mail_domain_bare, self.units)
+        configure_remote_units(self.config.mail_domain, self.units)
 
     def activate(self):
         activate_remote_units(self.units)
@@ -584,7 +584,7 @@ def deploy_chatmail(config_path: Path, disable_mail: bool, website_only: bool) -
     """
     config = read_config(config_path)
     check_config(config)
-    bare_host = config.mail_domain_bare
+    mail_domain = config.mail_domain
 
     if website_only:
         Deployment().perform_stages([WebsiteDeployer(config)])
@@ -635,7 +635,7 @@ def deploy_chatmail(config_path: Path, disable_mail: bool, website_only: bool) -
                     )
                     exit(1)
 
-    tls_deployer = get_tls_deployer(config, bare_host)
+    tls_deployer = get_tls_deployer(config, mail_domain)
 
     all_deployers = [
         ChatmailDeployer(config),
@@ -643,13 +643,13 @@ def deploy_chatmail(config_path: Path, disable_mail: bool, website_only: bool) -
         FiltermailDeployer(),
         JournaldDeployer(),
         UnboundDeployer(config),
-        TurnDeployer(bare_host),
+        TurnDeployer(mail_domain),
         IrohDeployer(config.enable_iroh_relay),
         tls_deployer,
         WebsiteDeployer(config),
         ChatmailVenvDeployer(config),
         MtastsDeployer(),
-        OpendkimDeployer(config.mail_domain),
+        OpendkimDeployer(mail_domain),
         # Dovecot should be started before Postfix
         # because it creates authentication socket
         # required by Postfix.

cmdeploy/src/cmdeploy/dovecot/deployer.py

@@ -73,7 +73,7 @@ class DovecotDeployer(Deployer):
         )
 
     def configure(self):
-        configure_remote_units(self.config.mail_domain_bare, self.units)
+        configure_remote_units(self.config.mail_domain, self.units)
         config_restart, self.daemon_reload = _configure_dovecot(self.config)
         self.need_restart |= config_restart
 

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

@@ -7,7 +7,6 @@ listen = 0.0.0.0
 protocols = imap lmtp
 
 auth_mechanisms = plain
-auth_username_chars = abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ01234567890.-_@[]
 
 {% if debug == true %}
 auth_verbose = yes

cmdeploy/src/cmdeploy/filtermail/deployer.py

@@ -7,7 +7,7 @@ from cmdeploy.basedeploy import Deployer, get_resource
 
 
 class FiltermailDeployer(Deployer):
-    services = ["filtermail", "filtermail-incoming", "filtermail-transport"]
+    services = ["filtermail", "filtermail-incoming"]
     bin_path = "/usr/local/bin/filtermail"
     config_path = "/usr/local/lib/chatmaild/chatmail.ini"
 
@@ -26,10 +26,10 @@ class FiltermailDeployer(Deployer):
             return
 
         arch = host.get_fact(facts.server.Arch)
-        url = f"https://github.com/chatmail/filtermail/releases/download/v0.6.4/filtermail-{arch}"
+        url = f"https://github.com/chatmail/filtermail/releases/download/v0.6.1/filtermail-{arch}"
         sha256sum = {
-            "x86_64": "5295115952c72e4c4ec3c85546e094b4155a4c702c82bd71fcdcb744dc73adf6",
-            "aarch64": "6892244f17b8f26ccb465766e96028e7222b3c8adefca9fc6bfe9ff332ca8dff",
+            "x86_64": "48b3fb80c092d00b9b0a0ef77a8673496da3b9aed5ec1851e1df936d5589d62f",
+            "aarch64": "c65bd5f45df187d3d65d6965a285583a3be0f44a6916ff12909ff9a8d702c22e",
         }[arch]
         self.need_restart |= files.download(
             name="Download filtermail",

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

@@ -1,11 +0,0 @@
-[Unit]
-Description=Chatmail transport service
-
-[Service]
-ExecStart={{ bin_path }} {{ config_path }} transport
-Restart=always
-RestartSec=30
-User=vmail
-
-[Install]
-WantedBy=multi-user.target

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

@@ -73,7 +73,7 @@ http {
 
 		access_log syslog:server=unix:/dev/log,facility=local7;
 
-		location /mxdeliv {
+		location /mxdeliv/ {
 		    proxy_pass http://127.0.0.1:{{ config.filtermail_http_port_incoming }};
 		}
 

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

@@ -54,16 +54,14 @@ smtpd_tls_exclude_ciphers = aNULL, RC4, MD5, DES
 tls_preempt_cipherlist = yes
 
 smtpd_relay_restrictions = permit_mynetworks permit_sasl_authenticated defer_unauth_destination
-myhostname = {{ config.postfix_myhostname }}
+myhostname = {{ config.mail_domain }}
 alias_maps = hash:/etc/aliases
 alias_database = hash:/etc/aliases
 
-# When postfix receives mail for $mydestination,
-# it hands it over to dovecot via $local_transport.
-mydestination = {{ config.mail_domain }}
-local_transport = lmtp:unix:private/dovecot-lmtp
-# postfix doesn't check whether local users exist or not:
-local_recipient_maps =
+# Postfix does not deliver mail for any domain by itself.
+# Primary domain is listed in `virtual_mailbox_domains` instead
+# and handed over to Dovecot.
+mydestination =
 
 relayhost = 
 {% if disable_ipv6 %}
@@ -81,6 +79,24 @@ inet_protocols = ipv4
 inet_protocols = all
 {% endif %}
 
+# Postfix does not try IPv4 and IPv6 connections
+# concurrently as of version 3.7.11.
+#
+# When relay has both A (IPv4) and AAAA (IPv6) records,
+# but broken IPv6 connectivity,
+# every second message is delayed by the connection timeout
+# <https://www.postfix.org/postconf.5.html#smtp_connect_timeout>
+# which defaults to 30 seconds. Reducing timeouts is not a solution
+# as this will result in a failure to connect to slow servers.
+#
+# As a workaround we always prefer IPv4 when it is available.
+# 
+# The setting is documented at
+# <https://www.postfix.org/postconf.5.html#smtp_address_preference>
+smtp_address_preference=ipv4
+
+virtual_transport = lmtp:unix:private/dovecot-lmtp
+virtual_mailbox_domains = {{ config.mail_domain }}
 lmtp_header_checks = regexp:/etc/postfix/lmtp_header_cleanup
 
 mua_client_restrictions = permit_sasl_authenticated, reject
@@ -93,12 +109,3 @@ smtpd_sender_login_maps = regexp:/etc/postfix/login_map
 # Do not lookup SMTP client hostnames to reduce delays
 # and avoid unnecessary DNS requests.
 smtpd_peername_lookup = no
-
-# Use filtermail-transport to relay messages.
-# We can't force postfix to split messages per destination,
-# when specifying a custom next-hop,
-# 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 }}
-lmtp-filtermail_initial_destination_concurrency=10000
-lmtp-filtermail_destination_concurrency_limit=10000

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

@@ -80,9 +80,8 @@ filter    unix -        n       n       -       -       lmtp
 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 smtpd_milters=unix:opendkim/opendkim.sock
   -o cleanup_service_name=authclean
-{% 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
@@ -101,8 +100,3 @@ filter    unix -        n       n       -       -       lmtp
 # cannot send unprotected Subject.
 authclean unix  n       -       -       -       0       cleanup
   -o header_checks=regexp:/etc/postfix/submission_header_cleanup
-
-lmtp-filtermail unix  -       -       y       -       10000       lmtp
-  -o syslog_name=postfix/lmtp-filtermail
-  -o lmtp_header_checks=
-  -o lmtp_tls_security_level=none

cmdeploy/src/cmdeploy/remote/rdns.py

@@ -64,11 +64,13 @@ def get_dkim_entry(mail_domain, pre_command, dkim_selector):
     )
 
 
-def query_dns(typ, domain):
+def query_dns(typ, domain, shell_exec=None):
+    if shell_exec is None:
+        shell_exec = shell
     # Get autoritative nameserver from the SOA record.
     soa_answers = [
         x.split()
-        for x in shell(
+        for x in shell_exec(
             f"dig -r -q {domain} -t SOA +noall +authority +answer", print=log_progress
         ).split("\n")
     ]
@@ -78,8 +80,27 @@ def query_dns(typ, domain):
     ns = soa[0][4]
 
     # Query authoritative nameserver directly to bypass DNS cache.
-    res = shell(f"dig @{ns} -r -q {domain} -t {typ} +short", print=log_progress)
-    return next((line for line in res.split("\n") if not line.startswith(";")), "")
+    return _dig_authoritative(ns, domain, typ, shell_exec=shell_exec)
+
+
+def _parse_dig_result(output):
+    """Return first non-comment, non-empty line from dig output, or empty string."""
+    lines = [line for line in output.split("\n") if not line.startswith(";")]
+    return next((line for line in lines if line.strip()), "")
+
+
+def _dig_authoritative(ns, domain, typ, shell_exec=None):
+    """Query authoritative NS, falling back to IPv4-only if default fails."""
+    if shell_exec is None:
+        shell_exec = shell
+
+    # limit timeout and tries to not hang on a broken default NS
+    cmd = f"dig @{ns} -r -q {domain} -t {typ} +short +timeout=10 +tries=2"
+    result = _parse_dig_result(shell_exec(cmd, print=log_progress))
+    if result:
+        return result
+    # Fallback: force IPv4 transport (handles broken IPv6 to NS)
+    return _parse_dig_result(shell_exec(cmd + " -4", print=log_progress))
 
 
 def check_zonefile(zonefile, verbose=True):

cmdeploy/src/cmdeploy/tests/online/test_0_login.py

@@ -89,11 +89,12 @@ def test_concurrent_logins_same_account(
         assert login_results.get()
 
 
-def test_no_vrfy(cmfactory, chatmail_config, maildomain):
+def test_no_vrfy(cmfactory, chatmail_config):
     ac = cmfactory.get_online_account()
     addr = ac.get_config("addr")
+    domain = chatmail_config.mail_domain
 
-    s = smtplib.SMTP(maildomain)
+    s = smtplib.SMTP(domain)
     s.starttls()
 
     s.putcmd("vrfy", f"wrongaddress@{chatmail_config.mail_domain}")

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

@@ -8,7 +8,6 @@ import pytest
 
 from cmdeploy import remote
 from cmdeploy.cmdeploy import get_sshexec
-from chatmaild.config import is_valid_ipv4
 
 
 class TestSSHExecutor:
@@ -22,8 +21,6 @@ class TestSSHExecutor:
         assert out == out2
 
     def test_perform_initial(self, sshexec, maildomain):
-        if is_valid_ipv4(maildomain):
-            pytest.skip(f"{maildomain} is not a domain")
         res = sshexec(
             remote.rdns.perform_initial_checks, kwargs=dict(mail_domain=maildomain)
         )

cmdeploy/src/cmdeploy/tests/online/test_2_deltachat.py

@@ -15,7 +15,7 @@ def imap_mailbox(cmfactory, ssl_context):
     (ac1,) = cmfactory.get_online_accounts(1)
     user = ac1.get_config("addr")
     password = ac1.get_config("mail_pw")
-    host = user.split("@")[1].strip("[").strip("]")
+    host = user.split("@")[1]
     mailbox = imap_tools.MailBox(host, ssl_context=ssl_context)
     mailbox.login(user, password)
     mailbox.dc_ac = ac1
@@ -178,7 +178,7 @@ def test_hide_senders_ip_address(cmfactory, ssl_context):
     chat.send_text("testing submission header cleanup")
     user2.wait_for_incoming_msg()
     addr = user2.get_config("addr")
-    host = addr.split("@")[1].strip("[").strip("]")
+    host = addr.split("@")[1]
     pw = user2.get_config("mail_pw")
     mailbox = imap_tools.MailBox(host, ssl_context=ssl_context)
     mailbox.login(addr, pw)

cmdeploy/src/cmdeploy/tests/plugin.py

@@ -10,8 +10,7 @@ import time
 from pathlib import Path
 
 import pytest
-from chatmaild.config import read_config, format_mail_domain, is_valid_ipv4
-
+from chatmaild.config import read_config
 
 conftestdir = Path(__file__).parent
 
@@ -59,12 +58,7 @@ def chatmail_config(pytestconfig):
 
 @pytest.fixture(scope="session")
 def maildomain(chatmail_config):
-    return chatmail_config.mail_domain_bare
-
-
-@pytest.fixture(scope="session")
-def maildomain_deliverable(maildomain):
-    return format_mail_domain(maildomain)
+    return chatmail_config.mail_domain
 
 
 @pytest.fixture(scope="session")
@@ -284,6 +278,7 @@ def gencreds(chatmail_config):
 
     def gen(domain=None):
         domain = domain if domain else chatmail_config.mail_domain
+        addr_domain = f"[{domain}]" if _is_ip(domain) else domain
         while 1:
             num = next(count)
             alphanumeric = "abcdefghijklmnopqrstuvwxyz1234567890"
@@ -297,7 +292,7 @@ def gencreds(chatmail_config):
             password = "".join(
                 random.choices(alphanumeric, k=chatmail_config.password_min_length)
             )
-            yield f"{user}@{domain}", f"{password}"
+            yield f"{user}@{addr_domain}", f"{password}"
 
     return lambda domain=None: next(gen(domain))
 
@@ -322,8 +317,7 @@ class ChatmailACFactory:
 
     def _make_transport(self, domain):
         """Build a transport config dict for the given domain."""
-        domain_deliverable = format_mail_domain(domain)
-        addr, password = self.gencreds(domain_deliverable)
+        addr, password = self.gencreds(domain)
         transport = {
             "addr": addr,
             "password": password,
@@ -332,7 +326,7 @@ class ChatmailACFactory:
             "imapServer": domain,
             "smtpServer": domain,
         }
-        if domain.startswith("_") or is_valid_ipv4(domain):
+        if self.chatmail_config.tls_cert_mode == "self":
             transport["certificateChecks"] = "acceptInvalidCertificates"
         return transport
 
@@ -347,8 +341,7 @@ class ChatmailACFactory:
         accounts = []
         for _ in range(num):
             account = self.dc.add_account()
-            domain_deliverable = format_mail_domain(domain)
-            addr, password = self.gencreds(domain_deliverable)
+            addr, password = self.gencreds(domain)
             if _is_ip(domain):
                 # Use DCLOGIN scheme with explicit server hosts,
                 # matching how madmail presents its addresses to users.

cmdeploy/src/cmdeploy/tests/test_cmdeploy.py

@@ -39,14 +39,6 @@ class TestCmdline:
         out, err = capsys.readouterr()
         assert "deleting config file" in out.lower()
 
-    def test_dns_skip_on_ip(self, capsys, tmp_path, monkeypatch):
-        monkeypatch.delenv("CHATMAIL_INI", raising=False)
-        inipath = tmp_path / "chatmail.ini"
-        assert main(["init", "--config", str(inipath), "1.3.3.7"]) == 0
-        assert main(["dns", "--config", str(inipath)]) == 0
-        out, err = capsys.readouterr()
-        assert out == "[WARNING] 1.3.3.7 is not a domain, skipping DNS checks.\n"
-
 
 def test_www_folder(example_config, tmp_path):
     reporoot = importlib.resources.files(__package__).joinpath("../../../../").resolve()

cmdeploy/src/cmdeploy/tests/test_dns.py

@@ -214,3 +214,59 @@ class TestZonefileChecks:
         assert not mockout.captured_red
         assert "correct" in mockout.captured_green[0]
         assert not mockout.captured_red
+
+
+class TestDigAuthoritative:
+    @pytest.fixture
+    def dig_auth(self):
+        """Helper that calls _dig_authoritative with a recording shell function."""
+        calls = []
+
+        def run(first_result, ipv4_result=None):
+            def shell(cmd, print=print):
+                calls.append(cmd)
+                if "-4" in cmd:
+                    return ipv4_result or ""
+                return first_result
+
+            result = remote.rdns._dig_authoritative(
+                "ns1.example.", "example.com", "A", shell_exec=shell
+            )
+            return result, calls
+
+        return run
+
+    def test_ipv4_fallback_on_error(self, dig_auth):
+        """Fallback to -4 when first query returns only error lines."""
+        result, calls = dig_auth(
+            first_result=(
+                ";; communications error to 2a01:4f8:10a:1044::80#53: timed out\n"
+                ";; communications error to 2a01:4f8:10a:1044::80#53: timed out\n"
+            ),
+            ipv4_result="1.2.3.4",
+        )
+        assert len(calls) == 2
+        assert "-4" not in calls[0]
+        assert "-4" in calls[1]
+        assert result == "1.2.3.4"
+
+    def test_no_fallback_on_success(self, dig_auth):
+        """No -4 fallback when first query returns a valid answer."""
+        result, calls = dig_auth(first_result="1.2.3.4")
+        assert result == "1.2.3.4"
+        assert len(calls) == 1
+
+    def test_fallback_with_mixed_error_lines(self, dig_auth):
+        """Fallback triggers when output has only error lines mixed with empty."""
+        result, calls = dig_auth(
+            first_result=(
+                ";; communications error to 2a01:4f8::80#53: timed out\n"
+                "\n"
+                ";; communications error to 2a01:4f8::80#53: timed out\n"
+            ),
+            ipv4_result=";; some warning\n1.2.3.4",
+        )
+        assert len(calls) == 2
+        assert result == "1.2.3.4"
+
+

cmdeploy/src/cmdeploy/tests/test_helpers.py

@@ -1,10 +1,11 @@
-from pathlib import Path
+import importlib.resources
 
 from cmdeploy.www import build_webpages
 
 
 def test_build_webpages(tmp_path, make_config):
-    src_dir = (Path(__file__).resolve() / "../../../../../www/src").resolve()
+    pkgroot = importlib.resources.files("cmdeploy")
+    src_dir = pkgroot.joinpath("../../../www/src").resolve()
     assert src_dir.exists(), src_dir
     config = make_config("chat.example.org")
     build_dir = tmp_path.joinpath("build")

cmdeploy/src/cmdeploy/www.py

@@ -1,4 +1,5 @@
 import hashlib
+import importlib.resources
 import re
 import time
 import traceback
@@ -36,7 +37,7 @@ def prepare_template(source):
 
 
 def get_paths(config) -> (Path, Path, Path):
-    reporoot = (Path(__file__).resolve() / "../../../../").resolve()
+    reporoot = importlib.resources.files(__package__).joinpath("../../../").resolve()
     www_path = Path(config.www_folder)
     # if www_folder was not set, use default directory
     if config.www_folder == "":
@@ -132,7 +133,8 @@ def find_merge_conflict(src_dir) -> Path:
 
 
 def main():
-    reporoot = (Path(__file__).resolve() / "../../../../").resolve()
+    path = importlib.resources.files(__package__)
+    reporoot = path.joinpath("../../../").resolve()
     inipath = reporoot.joinpath("chatmail.ini")
     config = read_config(inipath)
     config.webdev = True

doc/source/getting_started.rst

@@ -14,6 +14,8 @@ Minimal requirements and prerequisites
 
 You will need the following:
 
+-  Control over a domain through a DNS provider of your choice.
+
 -  A Debian 12 **deployment server** with reachable SMTP/SUBMISSIONS/IMAPS/HTTPS ports.
    IPv6 is encouraged if available. Chatmail relay servers only require
    1GB RAM, one CPU, and perhaps 10GB storage for a few thousand active
@@ -26,11 +28,6 @@ You will need the following:
    (An ed25519 private key is required due to an `upstream bug in
    paramiko <https://github.com/paramiko/paramiko/issues/2191>`_)
 
--  Control over a domain through a DNS provider of your choice
-   (there is experimental support for :ref:`DNS-less relays <iponly>`).
-
-
-.. _setup:
 
 Setup with ``scripts/cmdeploy``
 -------------------------------------

doc/source/index.rst

@@ -19,4 +19,3 @@ Contributions and feedback welcome through the https://github.com/chatmail/relay
     reverse_dns
     related
     faq
-    iponly

doc/source/iponly.rst

@@ -1,29 +0,0 @@
-.. _iponly:
-
-Hosting without DNS records
-===========================
-
-.. note::
-
-   This option is experimental and might change without notice.
-
-In case you don't have a domain,
-for example in a local network,
-you can run a chatmail relay with only an IPv4 address as well.
-
-To deploy a relay without a domain,
-run ``cmdeploy init`` with only the IPv4 address
-during the :ref:`installation steps <setup>`,
-for example ``cmdeploy init 13.12.23.42``.
-
-Drawbacks
----------
-
-- your transport encryption will only use self-signed TLS certificates,
-  which are vulnerable against MITM attacks.
-  the chatmail core's end-to-end encryption should suffice in most scenarios though.
-
-- your messages will not be DKIM-signed;
-  experimentally, most chatmail relays accept non-DKIM-signed messages from IPv4-only relays,
-  but some relays might not accept messages from yours.
-

doc/source/overview.rst

@@ -153,7 +153,6 @@ Chatmail relay dependency diagram
         autoconfig.xml --- dovecot;
         postfix --- |10080|filtermail-outgoing;
         postfix --- |10081|filtermail-incoming;
-        postfix --- |10083|filtermail-transport;
         filtermail-outgoing --- |10025 reinject|postfix;
         filtermail-incoming --- |10026 reinject|postfix;
         dovecot --- |doveauth.socket|doveauth;
@@ -296,7 +295,9 @@ ensured by ``filtermail`` proxy.
 TLS requirements
 ~~~~~~~~~~~~~~~~
 
-Filtermail (used for delivery) requires a valid TLS.
+Postfix is configured to require valid TLS by setting
+`smtp_tls_security_level <https://www.postfix.org/postconf.5.html#smtp_tls_security_level>`_
+to ``verify``.
 
 You can test it by resolving ``MX`` records of your relay domain and
 then connecting to MX relays (e.g ``mx.example.org``) with