I’m an embedded computer systems designer. I have created a system based on Raspberry Pi that monitors certain aspects of a user’s home and sends a text to the user if certain conditions apply. In testing it I have found that texting from that system to my T-Mobile phone fails.
I have turned on external texting (for want of a better phrase) by contacting Customer service.
I have demonstrated that the system works fine in sending email to other destinations than my phone, and I have demonstrated that I can send a text to my phone from gmail. The problem, then, must be that even though I have loosened up security, T-Mobile seems to recognize and reject a text from msmtp in Linux.
How do we fix that? Is there a way to turn on error messaging in T-Mobile texting?