postfix: do lmtp via local instead of virtual transport

.github/workflows/ci.yaml

@@ -15,7 +15,7 @@ jobs:
         with:
           ref: ${{ github.event.pull_request.head.sha }}
       - name: download filtermail
-        run: curl -L https://github.com/chatmail/filtermail/releases/download/v0.2.0/filtermail-x86_64-musl -o /usr/local/bin/filtermail && chmod +x /usr/local/bin/filtermail
+        run: curl -L https://github.com/chatmail/filtermail/releases/download/v0.1.2/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

README.md

@@ -1,20 +1,25 @@
 
-# Chatmail relays for end-to-end encrypted email
+# No-DNS Chatmail relay
 
-Chatmail relay servers are interoperable Mail Transport Agents (MTAs) designed for: 
+With this branch, you don't need DNS at all,
+just a VPS with an IPv4 address,
+let's take `77.42.80.106` as an example.
+First, choose a random domain name (it doesn't need working DNS)
+and create a chatmail.ini config file:
 
--  **Zero State:** no private data or metadata collected, messages are auto-deleted, low disk usage
+```
+cmdeploy init [77.42.80.106]
+```
 
--  **Instant/Realtime:** sub-second message delivery, realtime P2P
-   streaming, privacy-preserving Push Notifications for Apple, Google, and Huawei;
+Then, in `cmdeploy/src/cmdeploy/postfix/transport`,
+remove the line corresponding to your relay,
+and add other for relays you know.
+Now you can deploy the relay to your IP address:
 
--  **Security Enforcement**: only strict TLS, DKIM and OpenPGP with minimized metadata accepted
+```
+cmdeploy run --skip-dns-check --ssh-host 77.42.80.106
+```
 
--  **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. 
-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)
+Finally, you can login with a `dclogin://` code like this, with the correct "domain name" and IP address:
 
+`dclogin:s0mer4nd0@[77.42.80.106]?p=w7i8da7h8uads92ycc2rufyl&v=1&ih=77.42.80.106&sh=77.42.80.106&sp=443&ip=443&ic=3&sc=3`

chatmaild/src/chatmaild/config.py

@@ -20,8 +20,7 @@ class Config:
     def __init__(self, inipath, params):
         self._inipath = inipath
         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_user_send_per_minute = int(params["max_user_send_per_minute"])
         self.max_mailbox_size = params["max_mailbox_size"]
         self.max_message_size = int(params.get("max_message_size", "31457280"))
         self.delete_mails_after = params["delete_mails_after"]
@@ -56,7 +55,6 @@ class Config:
         self.privacy_mail = params.get("privacy_mail")
         self.privacy_pdo = params.get("privacy_pdo")
         self.privacy_supervisor = params.get("privacy_supervisor")
-        self.tmpfs_index = params.get("tmpfs_index", "false").lower() == "true"
 
         # deprecated option
         mbdir = params.get("mailboxes_dir", f"/home/vmail/mail/{self.mail_domain}")
@@ -112,10 +110,10 @@ def get_default_config_content(mail_domain, **overrides):
 
     if mail_domain.endswith(".testrun.org"):
         override_inipath = inidir.joinpath("override-testrun.ini")
-        params = iniconfig.IniConfig(override_inipath)["params"]
+        privacy = iniconfig.IniConfig(override_inipath)["privacy"]
         lines = []
         for line in content.split("\n"):
-            for key, value in params.items():
+            for key, value in privacy.items():
                 value_lines = value.format(mail_domain=mail_domain).strip().split("\n")
                 if not line.startswith(f"{key} =") or not value_lines:
                     continue

chatmaild/src/chatmaild/expire.py

@@ -17,14 +17,14 @@ from chatmaild.config import read_config
 FileEntry = namedtuple("FileEntry", ("path", "mtime", "size"))
 
 
-def iter_mailboxes(basedir, maxnum, tmpfs_index):
+def iter_mailboxes(basedir, maxnum):
     if not os.path.exists(basedir):
         print_info(f"no mailboxes found at: {basedir}")
         return
 
     for name in os_listdir_if_exists(basedir)[:maxnum]:
         if "@" in name:
-            yield MailboxStat(basedir + "/" + name, name, tmpfs_index)
+            yield MailboxStat(basedir + "/" + name)
 
 
 def get_file_entry(path):
@@ -49,14 +49,11 @@ def os_listdir_if_exists(path):
 class MailboxStat:
     last_login = None
 
-    def __init__(self, basedir, name, tmpfs_index):
+    def __init__(self, basedir):
         self.basedir = str(basedir)
-        self.name = name
         self.messages = []
         self.extrafiles = []
         self.scandir(self.basedir)
-        if tmpfs_index:
-            self.scandir("/dev/shm/" + name)
 
     def scandir(self, folderdir):
         for name in os_listdir_if_exists(folderdir):
@@ -93,13 +90,11 @@ class Expiry:
         self.all_files = 0
         self.start = time.time()
 
-    def remove_mailbox(self, mboxdir, name):
+    def remove_mailbox(self, mboxdir):
         if self.verbose:
             print_info(f"removing {mboxdir}")
         if not self.dry:
             shutil.rmtree(mboxdir)
-            if self.config.tmpfs_index:
-                shutil.rmtree("/dev/shm/" + name)
         self.del_mboxes += 1
 
     def remove_file(self, path, mtime=None):
@@ -126,7 +121,7 @@ class Expiry:
         self.all_mboxes += 1
         changed = False
         if mbox.last_login and mbox.last_login < cutoff_without_login:
-            self.remove_mailbox(mbox.basedir, mbox.name)
+            self.remove_mailbox(mbox.basedir)
             return
 
         mboxname = os.path.basename(mbox.basedir)
@@ -150,9 +145,6 @@ class Expiry:
             changed = True
         if changed:
             self.remove_file(f"{mbox.basedir}/maildirsize")
-        for file in mbox.extrafiles:
-            if "dovecot.index" in file.path.split("/")[-1] and file.size > 500 * 1024:
-                self.remove_file(file.path)
 
     def get_summary(self):
         return (
@@ -205,9 +197,7 @@ def main(args=None):
 
     maxnum = int(args.maxnum) if args.maxnum else None
     exp = Expiry(config, dry=not args.remove, now=now, verbose=args.verbose)
-    for mailbox in iter_mailboxes(
-        str(config.mailboxes_dir), maxnum, config.tmpfs_index
-    ):
+    for mailbox in iter_mailboxes(str(config.mailboxes_dir), maxnum=maxnum):
         exp.process_mailbox_stat(mailbox)
     print(exp.get_summary())
 

chatmaild/src/chatmaild/fsreport.py

@@ -159,7 +159,7 @@ def main(args=None):
 
     maxnum = int(args.maxnum) if args.maxnum else None
     rep = Report(now=now, min_login_age=int(args.min_login_age), mdir=args.mdir)
-    for mbox in iter_mailboxes(str(config.mailboxes_dir), maxnum, config.tmpfs_index):
+    for mbox in iter_mailboxes(str(config.mailboxes_dir), maxnum=maxnum):
         rep.process_mailbox_stat(mbox)
     rep.dump_summary()
 

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

@@ -11,12 +11,9 @@ mail_domain = {mail_domain}
 # Restrictions on user addresses
 #
 
-# email sending rate per user and minute
+# how many mails a user can send out per minute
 max_user_send_per_minute = 60
 
-# per-user max burst size for sending rate limiting (GCRA bucket capacity)
-max_user_send_burst_size = 10
-
 # maximum mailbox size of a chatmail address
 max_mailbox_size = 500M
 
@@ -48,9 +45,6 @@ passthrough_senders =
 # (space-separated, item may start with "@" to whitelist whole recipient domains)
 passthrough_recipients =
 
-# store index files in tmpfs (good for disk size and I/O, bad for ram)
-tmpfs_index = false
-
 # path to www directory - documented here: https://chatmail.at/doc/relay/getting_started.html#custom-web-pages
 #www_folder = www
 

chatmaild/src/chatmaild/ini/override-testrun.ini

@@ -1,6 +1,5 @@
-[params]
 
-tmpfs_index = true
+[privacy]
 
 passthrough_recipients = privacy@testrun.org echo@{mail_domain}
 

chatmaild/src/chatmaild/tests/test_expire.py

@@ -43,22 +43,20 @@ def create_new_messages(basedir, relpaths, size=1000, days=0):
 
 @pytest.fixture
 def mbox1(example_config):
-    addr = "mailbox1@example.org"
-    mboxdir = example_config.mailboxes_dir.joinpath(addr)
+    mboxdir = example_config.mailboxes_dir.joinpath("mailbox1@example.org")
     mboxdir.mkdir()
     fill_mbox(mboxdir)
-    return MailboxStat(mboxdir, addr, False)
+    return MailboxStat(mboxdir)
 
 
 def test_deltachat_folder(example_config):
     """Test old setups that might have a .DeltaChat folder where messages also need to get removed."""
-    addr = "mailbox1@example.org"
-    mboxdir = example_config.mailboxes_dir.joinpath(addr)
+    mboxdir = example_config.mailboxes_dir.joinpath("mailbox1@example.org")
     mboxdir.mkdir()
     mbox2dir = mboxdir.joinpath(".DeltaChat")
     mbox2dir.mkdir()
     fill_mbox(mbox2dir)
-    mb = MailboxStat(mboxdir, addr, False)
+    mb = MailboxStat(mboxdir)
     assert len(mb.messages) == 2
 
 
@@ -71,11 +69,7 @@ def test_filentry_ordering(tmp_path):
 
 
 def test_no_mailbxoes(tmp_path, capsys):
-    assert [] == list(
-        iter_mailboxes(
-            str(tmp_path.joinpath("notexists")), maxnum=10, tmpfs_index=False
-        )
-    )
+    assert [] == list(iter_mailboxes(str(tmp_path.joinpath("notexists")), maxnum=10))
     out, err = capsys.readouterr()
     assert "no mailboxes" in err
 
@@ -92,13 +86,13 @@ def test_stats_mailbox(mbox1):
 
     create_new_messages(mbox1.basedir, ["large-extra"], size=1000)
     create_new_messages(mbox1.basedir, ["index-something"], size=3)
-    mbox2 = MailboxStat(mbox1.basedir, mbox1.name, False)
+    mbox2 = MailboxStat(mbox1.basedir)
     assert len(mbox2.extrafiles) == 5
     assert mbox2.extrafiles[0].size == 1000
 
     # cope well with mailbox dirs that have no password (for whatever reason)
     Path(mbox1.basedir).joinpath("password").unlink()
-    mbox3 = MailboxStat(mbox1.basedir, mbox1.name, False)
+    mbox3 = MailboxStat(mbox1.basedir)
     assert mbox3.last_login is None
 
 

cmdeploy/src/cmdeploy/cmdeploy.py

@@ -89,6 +89,7 @@ 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
+    ssh_host = ssh_host.strip("[").strip("]")
     sshexec = get_sshexec(ssh_host)
     require_iroh = args.config.enable_iroh_relay
     if not args.dns_check_disabled:

cmdeploy/src/cmdeploy/deployers.py

@@ -17,7 +17,6 @@ from pyinfra.operations import apt, files, pip, server, systemd
 
 from cmdeploy.cmdeploy import Out
 
-from .acmetool import AcmetoolDeployer
 from .basedeploy import (
     Deployer,
     Deployment,
@@ -141,10 +140,6 @@ def _configure_remote_venv_with_chatmaild(config) -> None:
 
 
 class UnboundDeployer(Deployer):
-    def __init__(self, config):
-        self.config = config
-        self.need_restart = False
-
     def install(self):
         # Run local DNS resolver `unbound`.
         # `resolvconf` takes care of setting up /etc/resolv.conf
@@ -181,27 +176,6 @@ class UnboundDeployer(Deployer):
                 "unbound-anchor -a /var/lib/unbound/root.key || true",
             ],
         )
-        if self.config.disable_ipv6:
-            files.directory(
-                path="/etc/unbound/unbound.conf.d",
-                present=True,
-                user="root",
-                group="root",
-                mode="755",
-            )
-            conf = files.put(
-                src=get_resource("unbound/unbound.conf.j2"),
-                dest="/etc/unbound/unbound.conf.d/chatmail.conf",
-                user="root",
-                group="root",
-                mode="644",
-            )
-        else:
-            conf = files.file(
-                path="/etc/unbound/unbound.conf.d/chatmail.conf",
-                present=False,
-            )
-        self.need_restart |= conf.changed
 
     def activate(self):
         server.shell(
@@ -216,7 +190,6 @@ class UnboundDeployer(Deployer):
             service="unbound.service",
             running=True,
             enabled=True,
-            restarted=self.need_restart,
         )
 
 
@@ -553,14 +526,12 @@ def deploy_chatmail(config_path: Path, disable_mail: bool, website_only: bool) -
         files.line(
             name="Add 9.9.9.9 to resolv.conf",
             path="/etc/resolv.conf",
-            # Guard against resolv.conf missing a trailing newline (SolusVM bug).
-            line="\nnameserver 9.9.9.9",
+            line="nameserver 9.9.9.9",
         )
 
     port_services = [
         (["master", "smtpd"], 25),
         ("unbound", 53),
-        ("acmetool", 80),
         (["imap-login", "dovecot"], 143),
         ("nginx", 443),
         (["master", "smtpd"], 465),
@@ -592,10 +563,9 @@ def deploy_chatmail(config_path: Path, disable_mail: bool, website_only: bool) -
         LegacyRemoveDeployer(),
         FiltermailDeployer(),
         JournaldDeployer(),
-        UnboundDeployer(config),
+        UnboundDeployer(),
         TurnDeployer(mail_domain),
         IrohDeployer(config.enable_iroh_relay),
-        AcmetoolDeployer(config.acme_email, tls_domains),
         WebsiteDeployer(config),
         ChatmailVenvDeployer(config),
         MtastsDeployer(),

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

@@ -1,12 +1,13 @@
 ## Dovecot configuration file
 
 {% if disable_ipv6 %}
-listen = 0.0.0.0
+listen = *
 {% endif %}
 
 protocols = imap lmtp
 
 auth_mechanisms = plain
+auth_username_chars = abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ01234567890.-_@[]
 
 {% if debug == true %}
 auth_verbose = yes
@@ -68,11 +69,13 @@ userdb {
 ##
 
 # Mailboxes are stored in the "mail" directory of the vmail user home.
-{% if config.tmpfs_index %}
-mail_location = maildir:{{ config.mailboxes_dir }}/%u:INDEX=/dev/shm/%u
-{% else %}
 mail_location = maildir:{{ config.mailboxes_dir }}/%u
-{% endif %}
+
+# index/cache files are not very useful for chatmail relay operations 
+# but it's not clear how to disable them completely. 
+# According to https://doc.dovecot.org/2.3/settings/advanced/#core_setting-mail_cache_max_size
+# if the cache file becomes larger than the specified size, it is truncated by dovecot 
+mail_cache_max_size = 500K
 
 namespace inbox {
   inbox = yes
@@ -226,8 +229,8 @@ service anvil {
 }
 
 ssl = required
-ssl_cert = </var/lib/acme/live/{{ config.mail_domain }}/fullchain
-ssl_key = </var/lib/acme/live/{{ config.mail_domain }}/privkey
+ssl_cert = </etc/ssl/certs/ssl-cert-snakeoil.pem
+ssl_key = </etc/ssl/private/ssl-cert-snakeoil.key
 ssl_dh = </usr/share/dovecot/dh.pem
 ssl_min_protocol = TLSv1.3
 ssl_prefer_server_ciphers = yes

cmdeploy/src/cmdeploy/filtermail/deployer.py

@@ -14,10 +14,10 @@ class FiltermailDeployer(Deployer):
 
     def install(self):
         arch = host.get_fact(facts.server.Arch)
-        url = f"https://github.com/chatmail/filtermail/releases/download/v0.2.0/filtermail-{arch}-musl"
+        url = f"https://github.com/chatmail/filtermail/releases/download/v0.1.2/filtermail-{arch}"
         sha256sum = {
-            "x86_64": "1e5bbb646582cb16740c6dfbbca39edba492b78cc96ec9fa2528c612bb504edd",
-            "aarch64": "3564fba8605f8f9adfeefff3f4580533205da043f47c5968d0d10db17e50f44e",
+            "x86_64": "de7de6e011ffc06881d3a05fc9788e327ba2389219e77280ace38b429e11a5ce",
+            "aarch64": "a78fcdfb81eb3d9c8a8b6f84f6c0a75519b8be01aa25bd4617d72aae543992b4",
         }[arch]
         self.need_restart |= files.download(
             name="Download filtermail",

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

@@ -53,8 +53,8 @@ http {
 
 	ssl_protocols TLSv1 TLSv1.1 TLSv1.2 TLSv1.3;
 	ssl_prefer_server_ciphers on;
-	ssl_certificate /var/lib/acme/live/{{ config.domain_name }}/fullchain;
-	ssl_certificate_key /var/lib/acme/live/{{ config.domain_name }}/privkey;
+	ssl_certificate /etc/ssl/certs/ssl-cert-snakeoil.pem;
+	ssl_certificate_key /etc/ssl/private/ssl-cert-snakeoil.key;
 
 	gzip on;
 

cmdeploy/src/cmdeploy/postfix/deployer.py

@@ -60,7 +60,19 @@ class PostfixDeployer(Deployer):
             mode="644",
         )
         need_restart |= lmtp_header_cleanup.changed
-
+        # Transport map that discards messages to nine.testrun.org
+        transport_map = files.put(
+            src=get_resource("postfix/transport"),
+            dest="/etc/postfix/transport",
+            user="root",
+            group="root",
+            mode="644",
+        )
+        need_restart |= transport_map.changed
+        if transport_map.changed:
+            server.shell(
+                commands=["postmap /etc/postfix/transport"],
+            )
         # Login map that 1:1 maps email address to login.
         login_map = files.put(
             src=get_resource("postfix/login_map"),

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

@@ -15,12 +15,12 @@ readme_directory = no
 compatibility_level = 3.6
 
 # TLS parameters
-smtpd_tls_cert_file=/var/lib/acme/live/{{ config.mail_domain }}/fullchain
-smtpd_tls_key_file=/var/lib/acme/live/{{ config.mail_domain }}/privkey
+smtpd_tls_cert_file=/etc/ssl/certs/ssl-cert-snakeoil.pem
+smtpd_tls_key_file=/etc/ssl/private/ssl-cert-snakeoil.key
 smtpd_tls_security_level=may
 
 smtp_tls_CApath=/etc/ssl/certs
-smtp_tls_security_level=verify
+smtp_tls_security_level=encrypt
 # Send SNI extension when connecting to other servers.
 # <https://www.postfix.org/postconf.5.html#smtp_tls_servername>
 smtp_tls_servername = hostname
@@ -54,21 +54,18 @@ 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.mail_domain }}
 alias_maps = hash:/etc/aliases
 alias_database = hash:/etc/aliases
 
 # 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 =
+mydestination = {{ config.mail_domain }}
+local_transport = lmtp:unix:private/dovecot-lmtp
+local_recipient_maps =
 
 relayhost = 
-{% if disable_ipv6 %}
-mynetworks = 127.0.0.0/8
-{% else %}
 mynetworks = 127.0.0.0/8 [::ffff:127.0.0.0]/104 [::1]/128
-{% endif %}
 mailbox_size_limit = 0
 message_size_limit = {{config.max_message_size}}
 recipient_delimiter = +
@@ -79,14 +76,15 @@ inet_protocols = ipv4
 inet_protocols = all
 {% endif %}
 
-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
 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
 
+# Discard messages to nine.testrun.org
+transport_maps = hash:/etc/postfix/transport
+
 # 1:1 map MAIL FROM to SASL login name.
 smtpd_sender_login_maps = regexp:/etc/postfix/login_map
 

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

@@ -86,7 +86,7 @@ filter    unix -        n       n       -       -       lmtp
 # 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_milters=unix:opendkim/opendkim.sock
+#  -o smtpd_milters=unix:opendkim/opendkim.sock
 
 # Cleanup `Received` headers for authenticated mail
 # to avoid leaking client IP.

cmdeploy/src/cmdeploy/postfix/transport

@@ -0,0 +1,2 @@
+nine.testrun.org discard:
+* :

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

@@ -190,18 +190,22 @@ def test_exceed_rate_limit(cmsetup, gencreds, maildata, chatmail_config):
         "encrypted.eml", from_addr=user1.addr, to_addr=user2.addr
     ).as_string()
 
-    start = time.time()
-    for i in range(chatmail_config.max_user_send_per_minute * 3):
-        print("Sending mail", str(i + 1), "at", time.time() - start, "s.")
+    timestamps = []
+    i = 0
+    while len(timestamps) <= chatmail_config.max_user_send_per_minute * 1.7:
+        print("Sending mail", str(i))
+        i += 1
         try:
             user1.smtp.sendmail(user1.addr, [user2.addr], mail)
+            timestamps.append(time.time())
         except smtplib.SMTPException as e:
-            if i < chatmail_config.max_user_send_burst_size:
+            if len(timestamps) < chatmail_config.max_user_send_per_minute:
                 pytest.fail(f"rate limit was exceeded too early with msg {i}")
             outcome = e.recipients[user2.addr]
             assert outcome[0] == 450
             assert b"4.7.1: Too much mail from" in outcome[1]
             return
+        timestamps[:] = [ts for ts in timestamps if ts >= (time.time() - 60)]
     pytest.fail("Rate limit was not exceeded")
 
 

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

@@ -1,4 +0,0 @@
-# Managed by cmdeploy: disable IPv6 in unbound.
-server:
-  interface: 127.0.0.1
-  do-ip6: no

doc/source/overview.rst

@@ -42,11 +42,6 @@ The deployed system components of a chatmail relay are:
 -  Dovecot_ is the Mail Delivery Agent (MDA) and
    stores messages for users until they download them
 
--  `filtermail <https://github.com/chatmail/filtermail>`_
-   prevents unencrypted email from leaving or entering the chatmail
-   service and is integrated into Postfix’s outbound and inbound mail
-   pipelines.
-
 -  Nginx_ shows the web page with privacy policy and additional information
 
 -  `acmetool <https://hlandau.github.io/acmetool/>`_ manages TLS
@@ -90,6 +85,11 @@ short overview of ``chatmaild`` services:
    <https://doc.dovecot.org/2.3/configuration_manual/authentication/dict/#complete-example-for-authenticating-via-a-unix-socket>`_
    to authenticate logins.
 
+-  `filtermail <https://github.com/chatmail/relay/blob/main/chatmaild/src/chatmaild/filtermail.py>`_
+   prevents unencrypted email from leaving or entering the chatmail
+   service and is integrated into Postfix’s outbound and inbound mail
+   pipelines.
+
 -  `chatmail-metadata <https://github.com/chatmail/relay/blob/main/chatmaild/src/chatmaild/metadata.py>`_
    is contacted by a `Dovecot lua
    script <https://github.com/chatmail/relay/blob/main/cmdeploy/src/cmdeploy/dovecot/push_notification.lua>`_