Looking for a bit of advice diagnosing this... let's assume my personal email address is email@example.com. The unforgettable.com domain is associated with mail.com - I use it as a forwarding service to my Google mail account firstname.lastname@example.org. Last weekend, several friends & colleagues told me that my email was bouncing. It appeared to be a transient thing as by the time I got to a PC, it appeared to be working fine.
However, I'm the author of www.whatpub.org and this system regularly sends out email summaries to users. It's ASP.NET v3/VB.NET based. Email is working fine with everyone else's email addresses except mine. They were just disappearing. Each time www.whatpub.org sends out an email address, it cc's it to another email account at the same time. These cc'd copies always got through.
In a flash of inspriation, I remembered that I could configure mail.com to keep a copy of the emails it forwards - so I turned that on and tried a test. This had to be a flash of inspiration as mail.com support haven't singularly failed to reply to any of my posts on the ticket I raised.
Voila - after a while, a non-delivery report arrived in the inbox on mail.com. This is the key bit from the NDR shown below.
The web app is hosted at webhost4life and their SMTP server is 18.104.22.168. There's a link to an AOL page (eh???) that suggests black listing.
[Edited as realised hadn't pasted the right bit]
I don't have enough knowledge of SMTP inner workings to fathom this out or understand those SMTP responses. I also haven't got much faith in mail.com or webhost4life to sort this out :-( That's why I've just registered a personal domain for me. Might be time for a change and get off all those spam lists!
Could not deliver message to the following recipient(s): Failed Recipient: email@example.com Reason: Remote host said: 440 4.4.0 MSG=: (DYN:T1) http://postmaster.info.aol.com/errors/421dynt1.html -- The header and top 20 lines of the message follows -- Received: from mx253o.mysite4now.com [22.214.171.124] by smtpgw02.myhostguy.com with SMTP; Wed, 23 Sep 2009 06:47:17 -0700 Received: from dedi561 (216-10-246-190.mysite4now.com [126.96.36.199]) by mx253o.mysite4now.com with SMTP; Wed, 23 Sep 2009 06:47:01 -0700 MIME-Version: 1.0 From: "HOPS Help" <firstname.lastname@example.org> To: email@example.com Date: 23 Sep 2009 06:47:00 -0700 Subject: WhatPub beer scores Content-Type: text/html; charset=us-ascii Content-Transfer-Encoding: quoted-printable