I have a bit of a strange issue, I configured SMS over SMTP on the Guest registration page for a customer. The customer configured mail server to allow Clearpass to be a relay. I've tested email and SMS successfully to multiple phone carries and email domains. The only service that does not work is AT&T. We cannot send the guest receipt to any phone with AT&T as a carrier. The carrier settings are default. Clearpass is running 6.3.6.
I cannot figure out why AT&T would not work, while Verizon, T-Mobile, etc. work fine.
Anybody come across this? This may have also been an issue prior to migrating from Amigopod to Clearpass Guest, but I can't seem to remember exactly when it started happening.
Any ideas what could cause this?
Thanks.