DoS bug in MessageASAP software

[forrie () TIAC NET (Forrest Aldrich)]

The popular MessageASAP software has in it an annoying bug
which can cause a nice SMTP flood during setup, under the
right circumstances.

In our case, we've had several incidents over the last week where
we began receiving hundreds upon hundreds of relay attempts,
by different users and all destined to "smtptest () messageasap com".

Because we control relaying ability, nothing could be sent, but our
logs filled up to very quickly.

The program appears to perform an MX lookup for the current domain
you have, and then attempts relaying off of those MX hosts.   In our case,
running large dial access pools which are used by different customers,
it began spamming our own servers.   The program doesn't recognize
RFC error codes (which we send), so it just keeps going and going....

One unfortunate side effect of this is, apart from wasting sysadmin time,
is that many people have had their accounts revoked due to violations of
Acceptable Use Policies.... even though they probably had no idea why.

A message has been sent to MessageASAP, in hopes they will code
better.

_F