Is it possible to create a Gmail filter that works on arbitrary headers?

Question

(Not a dup: this very similar question really asks about the DeliveredTo header).

Bugzilla provides a number of headers telling you why you received a mail, such as X-Bugzilla-Reason. How can I filter on arbitrary tags such as this one in Gmail?

Answer 1

Gmail doesn't do this. But if the emails do have text in the message, it can do it.

Answer 2

I agree with @Andrew - Gmail won't handle this on its own.

However, you could use an intermediary running procmail¹, preprocess the mail and add something to the subject, or change its sender, so that it can be filtered secondarily in Gmail.