DCC - Postfix MTA mail hub implementation question

Vernon Schryver vjs@calcite.rhyolite.com
Fri Aug 23 21:45:46 UTC 2002

> From: Paul Vixie <paul@vix.com>

> ...
> the milter API is actually very general and it's possible that postfix
> could just adopt it.
> ...

That's an excellent point.  You could probably borrow the filter side
of the sendmail milter code, or rewrite it to fit your own coding
style or standards.  I bet the MTA side would be almost as easy to
borrow or reverse engineer from the sendmail source.

As far as I can see, there is nothing in the Milter protocol or
filter API that is tied to sendmail with the possible exception of
the "macro" values that can be passed to the filter.

Note that the Milter protocol allows filters to be separated from
their MTAs by the whole Internet, because it supports TCP/IP as
well as UNIX domain sockets.

There are probably already more Milter filters of various sorts
than any other non-proprietary system, and more than most proprietary

There are two main problems I see with the Milter protocol.  One
is that it wants to do round trips on every header line, but that
could be patched with obvious pipelining hacks that would not break
compatibility.  The second is that filters can't get sendmail macro
values set during sendmail's consideration of the headers or body,
but that may be irrelevant.

Vernon Schryver    vjs@rhyolite.com

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