feat: Use filtermail for delivery to remote MTAs

Signed-off-by: Jagoda Ślązak <jslazak@jslazak.com>

.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/v0.6.1/filtermail-x86_64 -o /usr/local/bin/filtermail && chmod +x /usr/local/bin/filtermail
+        run: curl -L https://github.com/chatmail/filtermail/releases/download/v0.6.2/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

chatmaild/src/chatmaild/config.py

@@ -40,6 +40,9 @@ 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")

cmdeploy/src/cmdeploy/filtermail/deployer.py

@@ -7,7 +7,7 @@ from cmdeploy.basedeploy import Deployer, get_resource
 
 
 class FiltermailDeployer(Deployer):
-    services = ["filtermail", "filtermail-incoming"]
+    services = ["filtermail", "filtermail-incoming", "filtermail-transport"]
     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/v0.6.1/filtermail-{arch}"
+        url = f"https://github.com/chatmail/filtermail/releases/download/v0.6.2/filtermail-{arch}"
         sha256sum = {
-            "x86_64": "48b3fb80c092d00b9b0a0ef77a8673496da3b9aed5ec1851e1df936d5589d62f",
+            "x86_64": "0c68456d0999da727914e937cfce97fce6d3612f997438f536f4224c839f0ace",
-            "aarch64": "c65bd5f45df187d3d65d6965a285583a3be0f44a6916ff12909ff9a8d702c22e",
+            "aarch64": "5ac6f0be433b1c1ee907e1c1c47304473737a40fb5456d082a60f9dbb1688c36",
         }[arch]
         self.need_restart |= files.download(
             name="Download filtermail",

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

@@ -0,0 +1,11 @@
+[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/postfix/main.cf.j2

@@ -79,22 +79,6 @@ 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
@@ -109,3 +93,10 @@ 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 }}

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

@@ -100,3 +100,8 @@ 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       -       -       lmtp
+  -o syslog_name=postfix/lmtp-filtermail
+  -o lmtp_header_checks=
+  -o lmtp_tls_security_level=none

doc/source/overview.rst

@@ -153,6 +153,7 @@ 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;
@@ -295,9 +296,7 @@ ensured by ``filtermail`` proxy.
 TLS requirements
 ~~~~~~~~~~~~~~~~
 
-Postfix is configured to require valid TLS by setting
+Filtermail (used for delivery) requires a valid TLS.
-`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