SMTP SMS to my ATT cell phone [email scrubbed] fails with 554 5.1.0 ... has no MX or A record , stat=service unavailable

Yes, the email is being rejected because ATT does not recognize the sending email domain. Perhaps your IT department didn’t change anything but your company email is no longer recognized as a legitimate email domain.

Hello, @USER000099. Thank you for reaching out to us about your email-to-text messages coming back rejected. We understand how important it is to be able to send and receive your email-to-text messages, especially if this is needed for work. 

That trend can be one of a couple of factors:

• The mobile number isn't provisioned to receive SMS. If you're not receiving any SMS messages then you will want to check that there hasn't been any recent changes to the account to stop the delivery of SMS messages.
• The end-user blocked the sender's address or domain. You will want to check that you haven't disabled SMTP messaging. That error message you're receiving means the recipient has blocked incoming email-to-text messages. That restriction will need to removed before these kind of messages can be successfully delivered to the recipient.

Also, try resolving that trend by composing a new email and enter the recipient's 10-digit wireless number, followed by @mms.att.net. For example, 5551234567@mms.att.net. It is likely that changing the format will resolve that trend on your device.

What's more, please be advised that the design of the SMTP gateway allows for personal or one-to-one messages. When using the SMTP gateway for one-to-multiple or group messaging it often replicates spam behavior and may be blocked or limited by AT&T network protection controls.

The SMTP gateway is subject to millions of abusive messages daily and AT&T employs technologies to protect our customers and block unsolicited messages.

Give this a try and let us know how this worked for you. 

TT, AT&T Community Specialist

@USER000099 Apparently ATTHelp can not issue another DM invite on a thread that already had one. You will need to open a new thread to get a new DM invite.

Hello Nelson can you please respond back I am still having the issue

Having this same issue with multiple FirstNET devices, all receiving the same massage from our Public Safety CAD system. This issue started today 5/17/2023. All settings are the same and haven't been changed for the last 3years. What's going on?