AT&T – US has scheduled a maintenance. 

Maintenance start time: 2022-10-12 03:00 UTC. 
Maintenance end time: 2022-10-12 10:00 UTC. 

Impact MT: Clients may experience delayed/rejected/failed Short Code SMS and MMS MT traffic towards AT&T
Impact MO: Clients may experience delayed/rejected/failed Short Code SMS and MMS MO traffic from AT&T
Impact DLR: Clients may experience delayed/rejected/failed Short Code SMS and MMS DLR traffic from AT&T