Long time Miab user and lurker in general (some great solutions here). I hope someone can provide some insight on an issue which is throwing me for a bit of a loop. I’ve explained my setup and problems below with an example.
I’ve setup Roundcube to forward email to an external account.
I also have all mail on the box setup to relay through Mandrill (postfix config).
The email relay works perfectly for all email originating from the box. instance.
The problem is that the copied (or redirected) emails arrive at Mandrill with the original senders email address. Because I don’t own these addresses I obviously can’t sign them correctly and Mandrill rejects them. If the original sender was from one of the domains under my control it works perfectly too (as I have set SPF/DMARC etc on Mandrill).
firstname.lastname@example.org sends an email to forwardingaddress@domain. Roundcube Sieve tells this email to go to email@example.com via copy/redirect. Since all outgoing email is relayed, Mandrill now tries to send this but uses firstname.lastname@example.org as the FROM email instead of forwardingaddress@domain which results in a failure because email@example.com is unsigned.
I believe Alento has had similar issues with this setup.
From what I understand using an alias in miab would produce the same result (will do further tests this evening).
Does anyone know of a preferred solution for this? Should I try create an exception on postfix NOT to relay for this one domain or account? I would prefer the least hacky option that is friendly with Miab upgrades but this is not imperative.