PHP mail() delays

I've noticed that on my server (which is using webppliance) a lot of mail is delayed ... people signing up on forums wait 2-5 hours sometimes to get mail for things like forum registration verifications .. the same problem exists in these forums I've noticed, but not to as much an extent (I'll get notice that someone replied to a topic like 20 min after they did it, I know because I see the reply long before the email comes).
Anyone know how to optimize or remove this problem? Does it exist in sendmail or in the actual php mail() function? my current sendmail_path in php.ini is the default

 

 

 

 

Top