How to inject headers into certain messages?
I was tasked with devising a way to inject certain headers into those messages submitted to our Sun Messaging Server which fit a given criteria.
One example is adding delivery- and read-confirmation request headers to messages originating from a document-workflow program (for some reason it doesn't add the headers and we can't change the program itself). This program uses an account on our mailserver for all email traffic, so the server should be able to modify any of these messages to add headers.
I believe writing a simple milter is one way to do this; is there anything more straightforward (perhaps a built-in function or some feature of Sieve milters?)
Also, which headers are standard/widespread for these notification requests?
So far I've found these strings as added by our various email clients, and most of them seem to be nonstandard:
Generate-Delivery-Report
X-Read-Notification
X-Confirm-Reading-To
Notice-Requested-Upon-Delivery-To
(Read-Receipt-To)
There are more to be found, which puzzles me and sets off - which ones name the headers to be set?