AT&T SMS over SMTP not working

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?



Michael Haring
If my answer is helpful, a Kudos is always appreciated!
Guru Elite

Re: AT

We’ve been seeing extremely long delays with AT&T and are suggesting that our customers move to Twilio. Lately the carriers seem to be treating SMS via email as best effort.

Tim Cappalli | Aruba Security
@timcappalli | | ACMX #367 / ACCX #480

Re: AT

Is there a guide that assists with integrating Twilio and Clearpass? Do you have some config examples that I may present to the customer?

Michael Haring
If my answer is helpful, a Kudos is always appreciated!

Re: AT



Take a look at the here in ASE, this should get you sorted.



Best Regards

ClearPass Product Manager

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Aruba Employee

Re: AT

As far as Twilio setup in ClearPass Guest goes, it is pretty strait forward. Under SMS Gateways, add a Twilio Gateway. Just enter your API username and Password for Twilio, then enter your SMS Source Address from Twilio in the following format: +1##########  (+country_code_area_code_number) For example, if your Source Address number was 408-867-5309, the SMS Source Address would look like +14088675309.


I also set the Country Code to 1 and Default Length to 10, since I am in the USA. This just makes it so that you can send an SMS with the format of 4088675309.


Zach Jennings

Re: AT

Thanks for the info. We are having the customer do packet captures to verify the issue lies with AT&T and not the ClearPass server. If anything pops out that might be helpful to others I will let everyone know. If all checks out we may be looking into something like Twilio.



Michael Haring
If my answer is helpful, a Kudos is always appreciated!
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