|Subject:||SMTP delivery retry on IIS 6.0|
|Date:||20 Nov 2006|
due to increased greylisting on remote MTAs i am seeing more and more
of my outbound SMTP messages ending up in the "badmail" directory.
it seems that if the remote MTA replies with "452 Too many recipients
received this hour,", IIS will either never retry at all, or will retry
2-3 times and then send it to badmail. as far as i know, error 452 is
temporary and IIS should continue to retry until the Expiration Timeout
is reached (2 days).
the problem seems to be triggered specifically by the "452" error
(which i have discovered is typical of Ironport anti-spam appliances).
other greylisting codes like 451 are properly queued and retried by IIS
6.0 until the message goes through.
anybody got any ideas on this?