Merge #2255

2255: Create a polite and turtle delivery queue to accommodate destinations that expect emails to be sent slowly r=mergify[bot] a=nextgens

## What type of PR?

Feature

## What does this PR do?

Create a polite and turtle delivery queue to accommodate destinations that expect emails to be sent slowly

### Related issue(s)
- closes #2213

## Prerequisites
Before we can consider review and merge, please make sure the following list is done and checked.
If an entry in not applicable, you can check it or remove it from the list.

- [x] In case of feature or enhancement: documentation updated accordingly
- [x] Unless it's docs or a minor change: add [changelog](https://mailu.io/master/contributors/workflow.html#changelog) entry file.


Co-authored-by: Florent Daigniere <nextgens@freenetproject.org>

core/postfix/conf/main.cf

@@ -80,7 +80,7 @@ virtual_mailbox_maps = ${podop}mailbox
 
 # Mails are transported if required, then forwarded to Dovecot for delivery
 relay_domains = ${podop}transport
-transport_maps = ${podop}transport
+transport_maps = lmdb:/etc/postfix/transport.map, ${podop}transport
 virtual_transport = lmtp:inet:{{ LMTP_ADDRESS }}
 
 # Sender and recipient canonical maps, mostly for SRS

core/postfix/conf/master.cf

@@ -15,6 +15,22 @@ outclean  unix n       -       n       -       0       cleanup
   -o header_checks=pcre:/etc/postfix/outclean_header_filter.cf
   -o nested_header_checks=
 
+# Polite policy
+polite      unix  -       -       n       -       -       smtp
+  -o syslog_name=postfix-polite
+  -o polite_destination_concurrency_limit=3
+  -o polite_destination_rate_delay=0
+  -o polite_destination_recipient_limit=20
+  -o polite_destination_concurrency_failed_cohort_limit=10
+
+# Turtle policy
+turtle      unix  -       -       n       -       -       smtp
+  -o syslog_name=postfix-turtle
+  -o turtle_destination_concurrency_limit=1
+  -o turtle_destination_rate_delay=1
+  -o turtle_destination_recipient_limit=5
+  -o turtle_destination_concurrency_failed_cohort_limit=10
+
 # Internal postfix services
 pickup    unix  n       -       n       60      1       pickup
 cleanup   unix  n       -       n       -       0       cleanup

core/postfix/start.py

@@ -74,9 +74,10 @@ if os.path.exists("/overrides/mta-sts-daemon.yml"):
 else:
     conf.jinja("/conf/mta-sts-daemon.yml", os.environ, "/etc/mta-sts-daemon.yml")
 
-if not os.path.exists("/etc/postfix/tls_policy.map.lmdb"):
+for policy in ['tls_policy', 'transport']:
-    open("/etc/postfix/tls_policy.map", "a").close()
+    if not os.path.exists(f'/etc/postfix/{policy}.map.lmdb'):
-    os.system("postmap /etc/postfix/tls_policy.map")
+        open(f'/etc/postfix/{policy}.map', 'a').close()
+        os.system(f'postmap /etc/postfix/{policy}.map')
 
 if "RELAYUSER" in os.environ:
     path = "/etc/postfix/sasl_passwd"

docs/faq.rst

@@ -476,6 +476,22 @@ Any mail related connection is proxied by nginx. Therefore the SMTP Banner is al
 
 .. _`1368`: https://github.com/Mailu/Mailu/issues/1368
 
+My emails are getting rejected, I am being told to slow down, what can I do?
+````````````````````````````````````````````````````````````````````````````
+
+Some email operators insist that emails are delivered slowly. Mailu maintains two separate queues for such destinations: ``polite`` and ``turtle``. To enable them for some destination you can creating an override at ``overrides/postfix/transport.map`` as follow:
+
+.. code-block:: bash
+
+   yahoo.com   polite:
+   orange.fr   turtle:
+
+Re-starting the smtp container will be required for changes to take effect.
+
+*Issue reference:* `2213`_.
+
+.. _`2213`: https://github.com/Mailu/Mailu/issues/2213
+
 My emails are getting defered, what can I do?
 `````````````````````````````````````````````
 
@@ -488,7 +504,7 @@ If delivery to a specific domain fails because their DANE records are invalid or
    domain.example.com   may
    domain.example.org   encrypt
 
-The syntax and options are as described in `postfix's documentation`_. Re-creating the smtp container will be required for changes to take effect.
+The syntax and options are as described in `postfix's documentation`_. Re-starting the smtp container will be required for changes to take effect.
 
 .. _`postfix's documentation`: http://www.postfix.org/postconf.5.html#smtp_tls_policy_maps
 

towncrier/newsfragments/2213.feature

@@ -0,0 +1 @@
+Create a polite and turtle delivery queue to accommodate destinations that expect emails to be sent slowly