I discovered this while trying to send friends URLs ending in .xyz. The texts appeared to be sent, but no one was receiving them. At first I assumed it was because the link was blacklisted somewhere along the line, but further experimenting showed that I cannot send a text containing the string ".xyz" anywhere in the message.
I am able to receive such texts though.
The phone is a moto g(7) power running Android 10. A friend has a Samsung Galaxy S10E and also can't send .xyz.
Sending other tlds such as ".com" etc works fine. Any guesses about what's going on?