Spam Filter ISP Forums : Rate Limit @ Hostgator & QueueIfDestinationError https://www.logsat.com/spamfilter/forums/ Fri, 13 Mar 2026 03:20:55 +0000 Wed, 30 Jun 2010 01:46:15 +0000 http://blogs.law.harvard.edu/tech/rss Web Wiz Forums 11.04 360 https://www.logsat.com/spamfilter/forums/RSS_post_feed.asp?TID=6842 <![CDATA[Spam Filter ISP Forums]]> https://www.logsat.com/spamfilter/forums/forum_images/web_wiz_forums.png https://www.logsat.com/spamfilter/forums/ <![CDATA[Rate Limit @ Hostgator & QueueIfDestinationError : Bad bad hostgator! I noticed another...]]> https://www.logsat.com/spamfilter/forums/forum_posts.asp?TID=6842&PID=13686&title=rate-limit-hostgator-queueifdestinationerror#13686 Author: yapadu
Subject: 6842
Posted: 30 June 2010 at 1:46am

Bad bad hostgator!  I noticed another issue with them recently.  One of their servers connected to one of ours and got a 421 from us for greylisting.

They bounced the email right away, did not retry or try a server with lower priority either.

These large ISP/hosting companies are tough to deal with!
]]> Wed, 30 Jun 2010 01:46:15 +0000 https://www.logsat.com/spamfilter/forums/forum_posts.asp?TID=6842&PID=13686&title=rate-limit-hostgator-queueifdestinationerror#13686 <![CDATA[Rate Limit @ Hostgator & QueueIfDestinationError : Ok, this was a tricky one, and...]]> https://www.logsat.com/spamfilter/forums/forum_posts.asp?TID=6842&PID=13684&title=rate-limit-hostgator-queueifdestinationerror#13684 Author: LogSat
Subject: 6842
Posted: 30 June 2010 at 1:25am

Ok, this was a tricky one, and I should have caught it from your initial post:

Originally posted by yapadu yapadu wrote:

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.

Note how the initial reply line (the initial reply is the one that matters) has the digits 451 followed by a dash and then a description. From RFC 2821, which is the standard to which all SMTP server *must* abide to, the following section states:

2.4 General Syntax Principles and Transaction Model

   SMTP commands and replies have a rigid syntax.  All commands begin
   with a command verb.  All Replies begin with a three digit numeric
   code.  In some commands and replies, arguments MUST follow the verb
   or reply code.  Some commands do not accept arguments (after the
   verb), and some reply codes are followed, sometimes optionally, by
   free form text.  In both cases, where text appears, it is separated
   from the verb or reply code by a space character. 

This means that hostgator's server is in violation of RFC, as the response should have been:

451 The server has reached its limit for processing requests from your host.

With a [space] instead of the [-] after the 451. The second line in orange that they output:
451 Please try again later.
does have, correctly, a space, but that is too late, as it is the line above that is considered the reply, and it does not follow RFC. At that point, the reply is invalid as it does not contain a valid numeric code, and thus SpamFilter does not recognize the 451 as such.



Edited by LogSat - 30 June 2010 at 1:28am]]> Wed, 30 Jun 2010 01:25:44 +0000 https://www.logsat.com/spamfilter/forums/forum_posts.asp?TID=6842&PID=13684&title=rate-limit-hostgator-queueifdestinationerror#13684 <![CDATA[Rate Limit @ Hostgator & QueueIfDestinationError : This problem went away for a while,...]]> https://www.logsat.com/spamfilter/forums/forum_posts.asp?TID=6842&PID=13682&title=rate-limit-hostgator-queueifdestinationerror#13682 Author: yapadu
Subject: 6842
Posted: 29 June 2010 at 10:02am

This problem went away for a while, because we were able to get hostgator to whitelist our sending address.  However, they removed the whitelist and the problem is back again.]]> Tue, 29 Jun 2010 10:02:49 +0000 https://www.logsat.com/spamfilter/forums/forum_posts.asp?TID=6842&PID=13682&title=rate-limit-hostgator-queueifdestinationerror#13682 <![CDATA[Rate Limit @ Hostgator & QueueIfDestinationError : Here is a snippet of my .ini...]]> https://www.logsat.com/spamfilter/forums/forum_posts.asp?TID=6842&PID=13681&title=rate-limit-hostgator-queueifdestinationerror#13681 Author: yapadu
Subject: 6842
Posted: 29 June 2010 at 9:59am

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]]> Tue, 29 Jun 2010 09:59:10 +0000 https://www.logsat.com/spamfilter/forums/forum_posts.asp?TID=6842&PID=13681&title=rate-limit-hostgator-queueifdestinationerror#13681 <![CDATA[Rate Limit @ Hostgator & QueueIfDestinationError : yapadu,Could you please zip us...]]> https://www.logsat.com/spamfilter/forums/forum_posts.asp?TID=6842&PID=13652&title=rate-limit-hostgator-queueifdestinationerror#13652 Author: LogSat
Subject: 6842
Posted: 05 June 2010 at 2:14pm

yapadu,

Could you please zip us a section of SpamFilter's activity logfile that contains the entries to one such email, so we can take a look? The setting you set to "1" should indeed cause the email to be queued, without a bounce back to be created.
]]> Sat, 05 Jun 2010 14:14:43 +0000 https://www.logsat.com/spamfilter/forums/forum_posts.asp?TID=6842&PID=13652&title=rate-limit-hostgator-queueifdestinationerror#13652 <![CDATA[Rate Limit @ Hostgator & QueueIfDestinationError : Hi have been noticing over the...]]> https://www.logsat.com/spamfilter/forums/forum_posts.asp?TID=6842&PID=13649&title=rate-limit-hostgator-queueifdestinationerror#13649 Author: yapadu
Subject: 6842
Posted: 04 June 2010 at 9:44pm

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?
]]> Fri, 04 Jun 2010 21:44:15 +0000 https://www.logsat.com/spamfilter/forums/forum_posts.asp?TID=6842&PID=13649&title=rate-limit-hostgator-queueifdestinationerror#13649