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Setup postfix exclusively for local delivery

sz flag
Link64

For development purposes I wanted an smtp server, that simply places all mails into a local mailbox. To achieve this, I tried to setup a minimal postfix system.

# master.cf
smtp      inet       n  - n -     - smtpd
cleanup   unix       n  - n -     0 cleanup
qmgr      unix       n  - n 300   1 qmgr
rewrite   unix       -  - n -     - trivial-rewrite
bounce    unix       -  - n -     0 bounce
defer     unix       -  - n -     0 bounce
trace     unix       -  - n -     0 bounce
verify    unix       -  - n -     1 verify
error     unix       -  - n -     - error
retry     unix       -  - n -     - error
discard   unix       -  - n -     - discard
local     unix       -  n n -     - local
scache    unix       -  - n -     1 scache
proxymap  unix       -  - - -     1 proxymap
postlog   unix-dgram n  - n -     1 postlogd

# main.cf
compatibility_level = 3.7
queue_directory = /var/spool/postfix
command_directory = /usr/bin
daemon_directory = /usr/lib/postfix/bin
data_directory = /var/lib/postfix
mail_owner = postfix
inet_protocols = ipv4
unknown_local_recipient_reject_code = 550

mydestination = localhost
alias_maps = regexp:{{/.*/ mytargetuser@localhost}}
alias_database = $alias_maps

Talking to smtpd is no problem. I get successful responses through the entire conversation, however in the end, postfix tries to use smtp to deliver the mail, which is not enabled:

postfix/smtpd: connect from myhost.mydomain[127.0.0.1]
postfix/smtpd: 8D548E40850: client=myhost.mydomain[127.0.0.1]
postfix/cleanup: 8D548E40850: message-id=<20220506145639.8D548E40850@myhost>
postfix/qmgr: 8D548E40850: from=<[email protected]>, size=408, nrcpt=1 (queue active)
postfix/qmgr: warning: connect to transport private/smtp: Connection refused
postfix/error: 8D548E40850: to=<[email protected]>, relay=none, delay=30, delays=30/0/0/0.01, dsn=4.3.0, status=deferred (mail transport unavailable)

Any clue, why alias_maps is not working as I indended to use it here?

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anx avatar Server
fr flag
anx

The (local) alias maps are consulted after determining that the destination is local.

But you told Postfix that only localhost is a local destination, do you also need to adjust your mydestination setting. If any destination is local, this should do the trick:

mydestination=static:all
  • Consider also setting relay_transport=error to make both configuration intent and error handling immediately obvious. You do not want to relay with such configuration.
  • Consider leaving inet_protocols unset (default) and setting inet_interfaces=loopback-only to only serve clients from the very system it is running on. You do not want to receive mail from the wider internet with such configuration.
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sz flag
Link64
`mydestination=static:anything` works here, which resolves the original problem, thanks. Turns out my attempt was not working either way since the `alias_maps` lookup is recursive and it will end in an infinite loop where it tries to resolve the username. Empty `alias_maps`, `local_recipient_maps` and `luser_relay = myuser` is what does what I was trying to accomplish
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