System notification emails: Fax, VM, etc

I recently discovered that I have stopped receiving my email notifications when I receive a VM or a fax. I have rebooted the system, changed email addresses, ensured they aren't getting flagged as junk, etc. I'm still not receiving them. Everything else seems to work fine. Any ideas what I need to look into to fix this?

FreePBX
PBX Firmware: 6.12.65-30
PBX Service Pack: 1.0.0.0
Fax Pro module