[CentOS] Re: Postfix smtp freezing

>       I am currently running
> Centos 4.3
> postfix-2.2.10-1.RHEL4.2
> mailscanner-4.57.6-1
>

Your OS is out of date, but not terribly in the grand scheme of  
things.  This list probably remembers running CentOS 4.3 for quite a  
bit and it was rock solid.  I'd start with the SMTP error message.   
Try to be as specific as possible when posting to lists.  If the SMTP  
error is your symptom, give us the EXACT smtp error.  This may simply  
be a problem where your system hit a "default install" performance  
ceiling and/or ran out of resources.  Errors of this nature usually  
just require tweaking the config.

Regards,
Ken