apache stops connecting to postfix
 

I have a new server setup on Amazon EC2 from the official CentOS 6.4 AMI. I've installed LAMP, php 5.3.3, configured SELinux, firewall, etc. Everything seems to be working fine except today when I went to fire up my email newsletter. For some reason Postfix stops responding after about 500-700 emails go out. Initially I tried tweaking Postfix but that got me no where. I've reverted it back to original install and noticed when I restart Apache I can immediately send out another batch of emails.

The newsletter system is PHP/MySQL and worked fine on the previous system was mostly the same. There is nothing in the logs that would point me in the right direction, can anyone give me some tips to get me started? Thanks.

The error message I see in the newsletter software is "Could not execute /usr/sbin/sendmail.postfix" FYI.

Check to see if your newsletter software is using the inbuild PHP mail function or using an external helper program, if it's the latter then ensure that it's configured correctly, I would have expected /usr/sbin/sendmail as the mailer helper not /usr/sbin/sendmail.postfix

It seems to have been a CPU/memory issue. This site is on Amazon EC2 and a micro instance. I upgraded it to a small and the newsletter is sending out fine today. I'm guessing the system could not handle the additional load and was killing processes to keep itself (relatively) stable. So far so good with no more changes.