Not getting alert emails from OME

Hello - I have been using OME for a couple of months now.  I find that I am not consistently getting alerts emailed to me for Warning and Critical alerts.

I've tested it a number of times and when I do a test, it works fine.  But when it comes right down to it, I'm not getting any alerts when I need them, which is right away preferably.

Any ideas what may be going on?

Thanks,

KBeau