On Fri, 21 Jun 2002, David W. Tamkin wrote:
I've heard that there are MTAs that can consult with per-user filter
rules (perhaps not as fancy as what procmail can do, but at least with
some rules) before giving an SMTP response code.
Sendmail 8.10+ can be compiled with an option called "milter" which allows
an external process (not any program -- it has to be one linked with the
milter library, which also gets built along with sendmail) to interact
with sendmail at various stages of the mail processing prior to to final
delivery to the local delivery agent. I think this is enabled by default
as of sendmail 8.12. There are a couple of Perl modules and other filters
available that can be plugged in to milter. E.g., google for MIMEDefang.
There are also several ways to plug in to qmail, exim, and postfix that
don't require special linkage.
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