How to report spam that appeared in Messages on iPhone marked "Text Message" & thus sent via carrier (e.g. AT&T) NOT Apple, & NOT from a phone #?
This kind of thing is almost impossible to block because, as you pointed out, the e-mail address is almost always forged. I have hundreds of e-mails blocked on my account. That being said...
How to block someone via the Messages on the iPhone or iPad
- Launch the Messages app from the Home screen of your iPhone or iPad.
- Tap the conversation of the person you're trying to block.
- Tap the info button in the top right corner.
- Tap the name of the contact.
- Tap Block Caller. ...
- Tap Block Contact.
This is courtesy of https://www.imore.com/how-mute-block-and-report-imessage-spam-iphone-and-ipad
Or...
How do I stop spam texts AT&T?
To report a spam SMS message received on your iPhone, you can forward the text to the number SPAM (7726). AT&T will reply with a text asking for the phone number of the person who sent the spam text message. Reply with the phone number and that's it.
To block a specific email address
Sign in to your AT&T Mobility account and create a Message Preferences account. Add email addresses to the block list by replying to the spam text with BLOCK in the reply message.
From... https://www.iphonefaq.org/archives/971823