[Dovecot] deliver command line options "visible" in sieve script

I use dovecot mailbox as destination of fetches from a few POP mailboxes. I would like to pass name of "source mailbox" to sieve script via deliver's command line option(s).

As I understand I should use -a "mailbox@domain". How it would be accessible in sieve script?

-- [pl>en: Andrew] Andrzej Adam Filip : anfi@onet.eu It is always the best policy to tell the truth, unless, of course, you are an exceptionally good liar. -- Jerome K. Jerome