I doubt to use SMTP-milter since it can't make modifications to the
envelope.
SMFIR_CHGFROM and SMFIR_ADDRCPT_PAR support exists since Postfix
2.6, four stable releases ago. Support for SMFIR_ADDRCPT/SMFIR_DELRCPT
exists even longer.
From MILTER_README: When you use the before-queue content filter for
incoming SMTP mail (see SMTPD_PROXY_README), Milter applications have
access only to the SMTP command information; they have no access to the
message header or body, and cannot make modifications to the message or
to the envelope.
Is this obsolete?
