@Gmail. Com Being Rejected by Messages/Textra

I send a lot of messages, from my computer, to my phone to use as reminders or when I have to send a long text. Takes me too long to do it on the phones keypad, so I do it via pc, send as a text to my phone and forward from there. Been doing this for many years.
About 3-4 weeks ago, my email messages stated bouncing back to gmail.
Here is the error message.
421 4.1.0 sender rejected AUP#CDRBL

I am on Sprint/T-Mobile.
I use , , to send the text/email.

Anyone else having this issue?