Wietse Venema:
> d:
> > ### individual header_checks for each user ###
>
> The header_checks request specifies solely the content of one message
> header. It does not specify any other information: no information about
> a previous header, no information about users, or any other information.
Postfix is not an email content management system. To implement
non-trivial content policies for Postfix, such as context-dependent
content rules, you need to use an external content filter. For
example, amavisd plugged into Postfix via the Milter protocol.
Wietse
