DKIM Signing With Wrong Domain?

mrbmi513

I have multiple websites on multiple domains running on the same web server. I have msmtp set up to send email via a special server account on domaina for all sites, and that account has sending permissions for the addresses it needs. However, mail with the from address of domainb gets signed using the key from domaina. Occasionally, the signing will work properly, but that’s the exception. Sending mail directly from a mailbox on domainb results in a properly signed message.

tl;dr: sending mail from acccount@domainb.com via the account server@domaina.com results in the message being signed by domaina.com’s DKIM key, not domainb.com’s DKIM key. Signs with the proper domain only some of the time.

mrbmi513

I found a solution to the problem, and it’s such a simple one that it’s worth sharing.
Don’t include from in the configuration for the account, and instead add the --read-envelope-from parameter to your msmtp command invocation. That sets the envelope from to be whatever the From: header is, and therefore signs correctly.