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Is it possible to exempt "MAILER DAEMON" messages from alias expansion or relaying?

Context: Let's illustrate the problem is on this trivial forward-all setup:

/etc/aliases
root: monitoring@domain.com

/etc/postfix/generic_maps
@host.local linuxmail@domain.com

/etc/postfix/main.cf
relayhost = [smtp.domain.com]:submission

When the relay breaks

  • regular cronjob tries to send e-mail From:root@host.local
  • it gets rewritten by aliases and encounters relaying failure
  • "MAILER DAEMON" sends warning e-mail To:root@host.local
  • it gets rewritten by aliases and encounters relaying failure
  • the errors uselessly clutter the queue

I'd like them delivered to local inbox, alerting administrators who log in.
How do I exempt the error mail from alias expansion and/or relaying?

user185953
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1 Answers1

1

1 Sane solution

/etc/postfix/main.cf
   bounce_queue_lifetime = 0
   notify_classes = bounce
   bounce_notice_recipient = bounces@<yourdomain.tld>
  • You may be tempted to disable bounce(8) service, but I expect that disables postmaster bounces.

For more details see the Drop undelivered MAILER-DAEMON and collect bounces in postfix

How it works:

  1. Undeliverable bounce messages are deleted
  2. A copy of all bounce messages is sent to bounces@<yourdomain.tld>

Drawbacks: 1) bounces@<yourdomain.tld> must be a non-redirected local inbox. 2) original bounce messages are deleted after the server attempts their useless delivery over the failed relay

2 Slightly Insane solution (untested)

/etc/postfix/main.cf
   sender_dependent_default_transport_maps = hash:sender_dependent_default_transport_maps
   virtual_mailbox_base = /var/spool/mail
   virtual_mailbox_maps = hash:/etc/postfix/virtual_mailbox_maps
   virtual_uid_maps = hash:/etc/postfix/virtual_uid_maps
   virtual_gid_maps = static:<GID_of_/var/spool/mail>
   #virtual_mailbox_domains = <yourdomain.tld> #MAYBE

sender_dependent_default_transport_maps
   MAILER-DAEMON@<yourdomain.tld> virtual:

/etc/postfix/virtual_uid_maps
   alice@<yourdomain.tld>   1000
   bob@<yourdomain.tld>     1002
   charlie@<yourdomain.tld> 1001

/etc/postfix/virtual_mailbox_maps
   alice@<yourdomain.tld>    alice/
   bob@<yourdomain.tld>      bob
   charlie@<yourdomain.tld>  charlie
  • Don't forget to $postmap all *_maps files after every change.

For more details see the virtual delivery agent manpage and collect bounces in postfix

How it works:

  1. sender_dependent_default_transport_maps forces bounce delivery by virtual: delivery agent ...
  2. ... which delivers the message to mailbox/maildir configured in virtual_*_maps

Drawbacks: 1) Untested. 2) Will never deliver to UID below virtual_minimum_uid. 3) virtual_*_maps must be manually kept in sync with existing user accounts

3 fully Insane solution

/etc/postfix/main.cf
   virtual_mailbox_base = /var/spool/mail
   virtual_mailbox_maps = hash:/etc/postfix/virtual_mailbox_maps
   virtual_uid_maps = hash:/etc/postfix/virtual_uid_maps
   virtual_gid_maps = static:<GID_of_/var/spool/mail>
   virtual_mailbox_domains = bounces.<yourdomain.tld>
   smtp_generic_maps = regexp:/etc/postfix/generic_maps
   sender_canonical_maps = regexp:/etc/postfix/canonical_sender_maps

/etc/postfix/virtual_uid_maps
   alice@bounces.<yourdomain.tld>   1000
   bob@bounces.<yourdomain.tld>     1002
   charlie@bounces.<yourdomain.tld> 1001

/etc/postfix/virtual_mailbox_maps
   alice@bounces.<yourdomain.tld>    alice/
   bob@bounces.<yourdomain.tld>      bob
   charlie@bounces.<yourdomain.tld>  charlie

/etc/postfix/generic_maps
   /@bounces./ @

/etc/postfix/canonical_sender_maps
   /^([^@]*)$/ $(1)@bounces.<yourdomain.tld>
   /^([^@]*)@/ $(1)@bounces.
  • Don't forget to $postmap all *_maps files after every change.

How it works:

  1. canonical_sender_maps adds "bounces." to senders of all locally queued mail
  2. If a message goes out by SMTP, smtp_generic_maps undoes the change
  3. If a message bounces, smtp_generic_maps does not apply ...
  4. ... and notification is delivered to virtual domain @bounces.<yourdomain.tld>...
  5. ... which delivers the message to mailbox/maildir configured in virtual_*_maps

For more details see the address rewriting overview

Drawbacks: 1) Insane. 2) Will never deliver to UID below virtual_minimum_uid 3) virtual_*_maps must be manually kept in sync with existing user accounts

user185953
  • 45
  • 6