Forwarding to external domains (like virtual aliases), redux

[omniError]

Previous discussions:
#118
#225
and probably more

I think the procedure for handling forwarded mail needs to be in-housed. There is another wrinkle to consider which is the resolution of multiple forwarders:

compliance@example.com -> legal@example.com
gdpr@example.com -> legal@example.com
privacy@example.com -> legal@example.com

then:
legal@example.com -> somebody@foreign-server.com

My understanding is there is no way to loop in sieve, although the forwarder definitions can be queried from a store (eg. a sqlite file). The above example thus needs some sort of resolution procedure to arrive at the real destination. There should be some logical limit on the depth that this can go to. The other concerns in the linked conversations about DKIM and so on are also relevant here.

Otherwise the round-about solution, if I understand this correctly, would be to run something like postfix with a lua script in front of Stalwart. Misses the point I think. Email is not my main wheelhouse so please correct me if I am wrong. Thanks!

[mdecimus]

The example you are describing can be implemented using two approaches:

1. Creating three mailing lists for compliance@example.com, gdpr@example.com and privacy@example.com that have legal@example.com as a member.
2. Add compliance@example.com, gdpr@example.com and privacy@example.com as an account alias for legal@example.com.

Then, using ManageSieve, you can create a script on the legal@example.com account that forwards messages to somebody@foreign-server.com.

[omniError]

My uninitiated view would be to have the mail server deal with the abstraction in the background and have a simpler list for the user of the list of forwarders that they can change all in one place. Would seem to be a lot less error prone in implementation and maintenance ("did we update the sieve script for alias no. 142?") particularly in large orgs.