Hello Stephan,
First of all, thank you for dovecot-sieve implementation.
I see that you are adding X-Sieve header to all outgoing e-mail in cmd-redirect.c
/* Prepend sieve version header (should not affect signatures) */ rfc2822_header_field_write(f, "X-Sieve", SIEVE_IMPLEMENTATION);
How do you look at adding one more header, for example X-Sieve-Forward-From:
Now, when redirect action is in use - mail forwards using sendmail command line interface. The problem that there is no suitable way to know which user's script has generate redirect. Received: header may contain envelope receiver but this is valid if only 1 "rcpt to:" command was specified on SMTP session. This invokes problem when forwarding mail to non-local domains, breaking such things like SPF. I'd like to setup SRS for fixing this, but I don't know sender("sieve local user") mail. Adding one header with valid local user e-mail address will fix this. Google add 2 headers for this - X-Forwarded-To: and X-Forwarded-For: .
What do you think about this ?