Is it possible to rewrite a subject line based on recipient domain?

[Chapter11]

My postfix machine accepts mail for several domains, and relays all of it on to internal mailservers. That works fine.

We are converting all of our mail to receive from a new domain, ie, "user@domain1.com" is also "user@domain2.com". Right now the world sends mail to user@domain1.com. We want to add some flag text to the subject lines of any mail sent to user@domain1.com, so users see an indication that this mail arrived on the old address. This should happen only for domain1.com-destined email, not any of the other domains I handle.

Possible or not?

 

[ericbrunson]

You could write a filter for it. Basically you accept the mail then use the content_filter to send it to a new service which can manipulate the mail anyway you like. Look for articles on how to set up spam and virus filtering and use those as a model. The FILTER_README distributed with postfix has all the instructions you should need, but there are also howtos on the net.