SMTP feed -- SMTP Fast Exploding External Deliverer for Sendmail


SMTPfeed is a SMTP delivery agent which is called by sendmail, and it
improves time required to complete delivery a message to huge number of
recipients. SMTPfeed is effective for delivery of large mailing lists.

Delay of delivery by using sendmail causes by the fact that implementation
of SMTP delivery routine in sendmail processes all delivery in a series.
By this reason,  when it takes long time for delivery to one recipient
which is in a huge list, delivery to following recipients is greatly
influenced.

To avoid such a problem, delivery agents should be implemented so that
a delivery is not influenced by preceding delivery -- DNS queries should
be processed in parallel and SMTP deliveries should also be processed
in parallel.  Smtpfeed is the SMTP delivery agent for sendmail
implemented with this idea.

In current implementation as a first step, DNS queries are processed
in parallel, and then deliveries with SMTP in parallel are started.

Smtpfeed requires the LMTP(RFC2033) feature available since sendmail
8.9. But with other hacks into sendmail will make feature of SMTPfeed
more effective. A patch (3.4W) for the hacks is also available.
If you do not use special configurations which are introduced by the
patch, you may not want to apply the patch any more with sendmail 8.12
or later, which does not have limitation on number of recipients passed
from sendmail to smtpfeed.

Smtpfeed can not deliver huge messages because SMTPfeed stores all
information (includes message data) in memory. You should configure
sendmail.cf to deliver huge messages by internal SMTP delivery routine
of the sendmail.

- Motonori Nakamura
