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I am running an email server on and have recently started to have problems with remote delivery of emails sent using this server. Only about 5% of recipients are rejecting the emails, but they all share the following common message...

Remote host said: 554 Your access to this mail system has been rejected due to the sending MTA's poor reputation.

As far as I can tell my server is not on any blacklists, and it is set up correctly (the reverse DNS checks out and so on). I'm not even sure what the "Sending MTA" is, but I assume it's my server.

If anyone could shed any light on this I'd really appreciate it!

Here's the full bounce message...

Could not deliver message to the following recipient(s):

Failed Recipient:
Reason: Remote host said: 554 Your access to this mail system has been rejected due to the sending MTA's poor reputation. If you believe that this failure is in error, please contact the intended recipient via alternate means.

   -- The header and top 20 lines of the message follows --

Received: from [] by with SMTP;
   Thu, 3 Sep 2009 18:15:44 +0100
From: "Phil Wilks" 
Subject: Test 
Date: Thu, 3 Sep 2009 18:16:10 +0100
Organization: Fruity Solutions
MIME-Version: 1.0
Content-Type: multipart/alternative;
X-Mailer: Microsoft Office Outlook 12.0
Thread-Index: Acosujo9LId787jBSpS3xifcdmCF5Q==
Content-Language: en-gb
x-cr-hashedpuzzle: ADYN AzTI BO8c BsNW Cqg/ D10y E0H4 GYjP HZkV Hc9t ICru JPj7 Jd7O Jo7Q JtF2 KVjt;1;YwBoAGEAcgBsAG8AdAB0AGUALgBoAHUAbgB0AC0AZwByAHUAYgBiAGUAQABzAHUAbgBkAGEAeQAtAHQAaQBtAGUAcwAuAGMAbwAuAHUAawA=;Sosha1_v1;7;{F78BB28B-407A-4F86-A12E-7858EB212295};cABoAGkAbABAAGYAcgB1AGkAdAB5AHMAbwBsAHUAdABpAG8AbgBzAC4AYwBvAG0A;Thu, 03 Sep 2009 17:16:08 GMT;VABlAHMAdAA=
x-cr-puzzleid: {F78BB28B-407A-4F86-A12E-7858EB212295}

This is a multipart message in MIME format.

Content-Type: text/plain;
Content-Transfer-Encoding: 7bit
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up vote 8 down vote accepted

Your IP is blacklisted. Check here and here for more information.

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It appears that both those services look at the block of IP addresses (not sure how big a /24 block is). It appears that the person who owns the addresses just below me ( up to is sending a lot of email. Thanks for the links. – Phil Wilks Sep 3 '09 at 18:04
A /24 is a class-C network. Basically, it's anything in 77.245.64.x. – James Sneeringer Jan 7 '11 at 16:59

You will see here that this IP indeed does have a poor reputation. Upon closer inspection, the whole Class C listed in here. Don't know how many IPs you own in this range but they will all have problems sending mail. Contact your hosting provider for more information (and/or get a new block of IPs).

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Thanks, I think you are correct in that it's someone else in my Class C block that is causing the problems. I only own a few addresses in this range. Thanks for the info. – Phil Wilks Sep 3 '09 at 18:03

I believe it is an improper setting on the HOST with using

Most major ISP are listing thier Dynamic IP blocks in the PBL Database.

Therefore, when clients using a local mail program Outlook etc, the server is rejecting based on the PBL database (554 poor MTA rating). warns of the potential rejection of email based on a misconfiguration, from Authenticated email servers, certain types of web servers etc..

More info here (look for caution at the bottom of page) -

Here is the warning from Spamhaus:

Caution: Because the PBL lists normal customer IP space, do not use PBL on smarthosts or SMTP AUTH outbound servers for your own customers (or you risk blocking your own customers if their dynamic IPs are in the PBL). Do not use PBL in filters that do any ‘deep parsing’ of Received headers, or for other than checking IP addresses that hand off to your mailservers.

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protected by Michael Hampton Apr 14 at 16:00

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