I want to prepend a header with postfix to every outgoing mail from a specific domain. At the moment i use:
check_sender_access hash:/etc/postfix/prepend
with /etc/postfix/prepend:
my.domain PREPEND Header: value
this works quite nice, but when i send a e-mail to several recipients, then the header is added multiple times, one for each recipient, to each of the outgoing mails.
so when i send a mail to 4 persons, each of them receives a mail, which contains the header 4 times.
Best Answer
There is no "simple" solution for this. You need to define a second smtpd instance in master.cf, have it access it's own cleanup instance, and define a header_checks maps for this cleanup instance. Then, you'd prepend the header on some unique header present in that mail, i.e. message-id.