[Mimedefang] Adding filter_helo support

[David F. Skoll]

Philip Prindeville wrote:

>> But it breaks existing filters; we need the helo arg back.
>> And there's a good reason to pass HELO in filter_sender (and
>> filter_recipient, for that matter): You may WANT to defer your
>> HELO processing until later.  Our commercial products, for
>> example, let individual recipients decide if they want to use
>> various rules, which means we need to defer all processing
>> until at least RCPT.

> That's got to get hairy when you have multiple recipients specified.

It's hairy, but manageable.  Doing per-recipient content-filtering is
a lot hairier and less managable; we have to use hacks like
stream_by_domain or stream_by_recipient.  Unfortunately, that's just how
SMTP works.

Regards,

David.