Hi have been noticing over the past few days problems delivering email to some of hostgator's servers.  They are using some type of rate limit (I think they just started doing this recently), when you go over the limit you get this:

451-The server has reached its limit for processing requests from your host.
451 Please try again later.

Messages are automatically bounced back to sender when spamfilter gets this.  We have the following enabled:

QueueIfDestinationError400=1

It seems like with a 4xx error spamfilter should be holding the messages and trying again later, not rejecting them outright.

Is this a bug, or am I missing something?

Here is a snippet of my .ini file:

;Determines if SpamFilter should hold in the queue emails that were rejected by the destination SMTP server with an error in the 4xy range
QueueIfDestinationError400=1

;Determines if SpamFilter should hold in the queue emails that were rejected by the destination SMTP server with an error in the 5xy range
QueueIfDestinationError500=0

Here is a transaction from my log, trying to push an email to a server hosted with hostgator (who like to rate limit us!)

06/29/10 13:33:07:074 -- (1216) Detected TCP Connection: (SSL) 172.16.15.209
06/29/10 13:33:07:074 -- (1216) Connection from: 172.16.15.209
06/29/10 13:33:08:840 -- (1216) User authenticated with AUTH LOGIN: sender@undp.org
06/29/10 13:33:09:059 -- (1216) Received MAIL FROM: <sender@undp.org>
06/29/10 13:33:09:246 -- (1216) Received RCPT TO: dcam@example.com
06/29/10 13:33:09:246 -- (1216) Bypassed all rules for: dcam@example.com from sender@undp.org ( User authenticated with AUTH LOGIN)
06/29/10 13:33:11:090 -- (1216) Start virus scan
06/29/10 13:33:11:137 -- (1216) Starting queueing procedures
06/29/10 13:33:11:137 -- (1216) EMail from sender@undp.org to dcam@example.com was queued. Size: 21 KB, 21504 bytes
06/29/10 13:33:11:137 -- (4392) Sending email from sender@undp.org to dcam@example.com --
06/29/10 13:33:11:387 -- (4392) EMail from: sender@undp.org to: dcam@example.com --  was returned to sender - server error - example.com:25 said: The server has reached its limit for processing requests from your host. -- Please try again later. --
06/29/10 13:33:11:559 -- (4392) Error-email from sender@undp.org to dcam@example.com --  was forwarded to mail.undp.org:25
06/29/10 13:33:11:559 -- (4392) server error - example.com:25 said: The server has reached its limit for processing requests from your host. -- Please try again later. --

At that point the message is bounced.  The bounce says:

The specific error is:
server error - example.com:25 said: The server has reached its limit for processing requests from your host.
Please try again later.

I just tried a telnet session to the remote server to execute a delivery attempt by hand to see what the message is, but they are not blocking us right this moment.


Edited by yapadu - 29 June 2010 at 10:00am

Edited by LogSat - 30 June 2010 at 1:28am