>One last note on this thread. While rereading the FAQ, I came across this
>which indicates qmail has brakes to keep from generating denial of service
>attacks.
>
>http://cr.yp.to/qmail/faq/efficiency.html
>
>Does qmail back off from dead hosts?
>Answer: Yes. qmail has three backoff features: ...
Qmail backs off very well, but doesn't work all that well with
sendmail under heavy load. The problem is that sendmail keeps
accepting connections even when it doesn't have enough system
resources to accept mail, and tends to thrash to death. (Qmail
systems usually use tcpserver which enforces a maximum number of
simultaneous connections rejecting any beyond that limit.) But since
sendmail doesn't reject connections, qmail can't tell that the
recipient system isn't responding.
Sendmail users tend to assume that anything sendmail does must be
right, and anything different must be wrong, so they often blame qmail
for opening "too many" connections. In reality, the connections could
just as easily come from any other mail system, of course.
--
John R. Levine, IECC, POB 727, Trumansburg NY 14886 +1 607 387 6869
[EMAIL PROTECTED], Village Trustee and Sewer Commissioner, http://iecc.com/johnl,
Member, Provisional board, Coalition Against Unsolicited Commercial E-mail
