Nagios Support Forum

That would be verizon, however your ISP likely limits smtp forwarding, specifically port 25 and may force you to use theirs, such as smtp.comcast.net which will then forward to verizon since the email should be [phone number]@vztext.com or something along those lines.

Got it.

Change mail to SMTP pointing to our Exchange server and it's working now.

Thanks, as usual, you guys rock!!!!!