I manage a few mail servers for my employer. We noticed that we are being blocked by T-Mobile (relay=tmo-east.mx.a.cloudfilter.net). We send a lot of messages to our customers' SMS gateway addresses daily.
As of today, all of our messages have started. On the servers we saw bouncing back with 421 sender rejected AUP#SNDR messages.
Is there any way you could whitelist our mail server IP addresses? I know you are making some changes to fight spam, but it is hurting our clients who want to get notified on new property listings.
I can email the logs to you at an appropriate email address or complete a whitelist form if you would like, along with a list of our mail server IP addresses.
Please assist us with this issue.