This WordPress has been failing to send email notifications of your comments to myself for some time now, the issue has been solved, let me explain how and probably more importantly, explain what was causing the issue.
First of all, I’ve fixed it using Callum Macdonald’s WP Mail SMTP plugin. This basically allows you to enter your own SMTP settings for sending mail rather than using the php mail() function.
Now I was unsure about using a third party plugin to do this but let me explain why it was necessary.
Like many people, I use Google Apps to host my emails, rather than my web hoster. This means that the MX records for the domain andybarratt.co.uk point to Gmail.
The problem I had was quite simple, everytime wordpress sent an email to my email address, it tried to send it through my web hoster. Well the server, trying to be a clever little server saw my domain name and immediately took that as meaning it didn’t need to leave the server, so it checked for my email address on the server, couldn’t find it and gave up. Now I have Macdonald’s Mail SMTP plugin to direct outgoing emails through Gmail’s server. Problem solved.
Hopefully this will help you, even though many had found this fix, I hadn’t seen many discuss this explanation, even though I could tell that many were using Google Apps for their emails.