Hi, I cannot find a previous discussion about this topic here on the mailing list.
We are running postfix instances for a big corporation, which delivers to MS Exchange / Exchange online backends. We now have gotten the requirement to mark all e-mails coming from external senders to mark in the subjects. I'm quite clear how to implement this, we have the infrastructure in place. I'm looking more for some experiences and pros/cons for doing this in postfix, or in Exchange. It will come nevertheless, I'm just looking to minimize damage and impact for the end user, and where to do this best. Has anyone doing this experienced problems with S/MIME mail? Does this maybe trigger spam detection, especially on an Exchange / Exchange Online backend more? Does DKIM break? Thanks for all the input on this topic! Best regards, Jens
