NovaRod

A customer of ours reported they have been unable to receive email from one of their business partners in Ontario, Canada (their datacenter is in Dallas, TX).

The error they are getting is:

Message is waiting at rentcentric.com for delivery to cosmicgeeks.com.

Message delivery has been delayed to the following recipients:
Recipient: [SMTP:xxxcosmicgeeks.com]
Reason: Remote SMTP Server Returned: 451 Could not complete sender verify callout

Message headers follow:

Received: from your4105e587b6 ([74.107.175.81]) by rentcentric.com with MailEnable ESMTP; Fri, 02 Mar 2007 17:08:03 -0500

From: "Marg, RentCentric-Support" <xxxrentcentric.com>
To: "'Barb Oshel'" <xxxcosmicgeeks.com>
Subject: FW: Message Delivery Delay - FREEHAULIN
Date: Fri, 2 Mar 2007 17:08:41 -0500
MIME-Version: 1.0
Content-Type: text/plain;
charset="us-ascii"
Content-Transfer-Encoding: 7bit
X-Mailer: Microsoft Office Outlook, Build 11.0.5510
thread-index: Acdc933Da9Iy8FqNQDeKCc3c2tzM6AAH3sdg
X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2900.3028

======================================

Anyone have an idea on this type of error? Looks like we are trying to reverse verify their address, but when we worked with them today, some of the domains on our server received the test emails just fine while cosmicgeeks and freehaulin.com never received the test emails.

Any help appreciated...oh yea! Ticket is open with Surpass Support!

__________________
Dedicated Server cosmicgeeks.com
Server Load

NovaRod

Update (paraphrased from other inputs):

Exim by default will check the senders email address and send a callback to the sending server to check and see if the users email address actually exists. In this case the sender's email server was not verifying the email address actually exists and so the email was being rejected.

We already tried to talk to the other end to correct the problem, but they were clueless..... So here we are......

I didn't want to turn off callouts to verify the existence of email senders so I did some digging and found that Exim allows the callout feature to check with a whitelist to see if a callout instruction should be ignored.

We have sender verification activated (and want to keep it that way), so looked to see if it’s possible to bypass sender verification for some addresses. Although we could have selected an individual email address, at this point, I selected whole domain (*trusteddomain.com).

We worked the solution we found at http://forums.cpanel.net/showthread.php?t=45370 that allows sender verification while “whitelisting” our trusted domain. After making the code modifications to the server, we tested the email functions externally and all is well.

The next step is to contact the sender and have some test emails sent to our server. At the rate it has been failing, it will be self evident whether or not this resolves their problem.

An important point: this is not a problem with our server. It is a problem with the sender's server that we are patching for the benefit of our customer.

__________________
Dedicated Server cosmicgeeks.com
Server Load