I used maildroid for years but Google has now blocked it wrt email. I discovered Android Thunderbird and installed it. It works fine with my Gmail account (sending and receiving). But maildroid still works for my account hosted on site5.com, but Android Thunderbird doesn't. It silently discards emails sent to external sites. I've been working with site5 support for days now. They finally tried to an external site and observed the problem. They have now been promising their internal advanced support team is working on it, but it has been many days and no success yet. I decided to try K-9 after I discovered it was the code base for Android Thunderbird. It fails in the same way. Then I found this from Jan 2023: https://tinyurl.com/29em92e6 This seems to be my problem exactly, and there was no followup that it was solved. Note that there is no problem with inbound email, only outbound. The outgoing SMTP server is named correctly and configured for port 465, SSL/TLS security, and the email account name on the site5 server is given correctly, and with its correct password. I think this may be broken in the Android Thunderbird and K-9 implementation. (btw, I installed Android Thunderbird on a different Pixel 7 as well, configured it, and it also had the same problem, so it wasn't a phone cache or bad install issue). Help! Thanks!