Andy Green wrote:
But, if anything else currently has
the ability to manage customizable helper processes and multiplex jobs
efficiently among them in a way that only requires mime and zip
unpacking to be done onces even if you scan multiple times, I'd be happy
to hear about it.
''Postfix before-queue Milter support
Introduction
Postfix version 2.3 introduces support for the Sendmail version 8
Milter (mail filter) protocol. This protocol is used by applications
that run outside the MTA to inspect SMTP events (CONNECT, DISCONNECT),
SMTP commands (HELO, MAIL FROM, etc.) as well as mail content. All this
happens before mail is queued.
The reason for adding Milter support to Postfix is that there exists a
large collection of applications, not only to block unwanted mail, but
also to verify authenticity (examples: Domain keys identified mail,
SenderID+SPF and Domain keys) or to digitally sign mail (examples:
Domain keys identified mail, Domain keys). Having yet another
Postfix-specific version of all that software is a poor use of human and
system resources.
Postfix version 2.4 implements all the requests of Sendmail version 8
Milter protocols up to version 4, including message body replacement
(body replacement is not available with Postfix version 2.3). See,
however, the workarounds and limitations sections at the end of this
document.
I suspect those limitations include not passing info about
authentication and encryption the same way as sendmail, and that would
keep it from working out-of-the-box with MimeDefang. At least I'm not
aware of anyone making it work yet. If I had a problem with sendmail
I'd probably put some effort into that.
I have been able to get Postfix to do what I want without too much of a
massive effort, whereas when I first tried to use Sendmail I though the
m4 config must be an April Fool's joke. I guess if mail is a large part
of what you do, you can ride over that kind of quirk and become and
"sendmail expert" and get the job done.
The basic part of sendmail configuration has been solved by including
the m4 macros for all the common situations that are invoked by a
one-line entry in sendmail.mc. As shipped in fedora, changes to
sendmail.mc will automatically rebuild sendmail.cf and take effect
whenever sendmail is restarted. And other than needing one change to
accept outside mail, the stock config shipped with fedora is good for
most internet situations. The aliases, access, mailertable, etc. files
are relatively straightforward to configure for your local situation.
Using MimeDefang solves the rest of the problem for additional
customization. When using it, you can simply write your site-specific
additions in a perl snippets that execute in the milter phases instead
of having to mess with the mailer's internal language or limitations.
Being able to verify recipients on a different machine via smtp before
accepting a message is a good example of that kind of extension.
--
Les Mikesell
lesmikesell@xxxxxxxxx
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