Error Emailing to Phone (email to text)

I’m attempting to email a text message with a JPG image (also tried an PDF).

I emailed to xxxxxxxxxx@tmomail.net

I received the following bounce back message in my email…

Message not delivered There was a problem delivering your message to 7024974598@tmomail.net. See the technical details below, or try resending in a few minutes.

The response from the remote server was: 550 5.1.1 server temporarily unavailable AUP#MXRT