Over the last year I have "up-graded" Gmail's SMTP server from "passwords"
to "app passwords". I am using app passwords on port 587 on about 10
ESP32s. Recently, on at least one device messages seem to find their
way to the SMTP server, BUT never make it to my Gmail email account.

Initially, for 2 or 3 of the devices I used the same app password without
problems. As I seemed to get some "lost mail" I started using individual
app passwords for each device. This does not seem to have helped.

I have read a bit on OAuth and using Firebase to monitor and control
devices. I do not want to control anything, so I am not too worried
about security.

Edit:
Using a verbose version of uMail I see a 235 returned which appears to be an auth error.

Updated to v1.25 Generic , modified umail.py to use ssl and now I get:

  File "ssl.py", line 1, in wrap_socket
  File "ssl.py", line 1, in wrap_socket
OSError: (-29184, 'MBEDTLS_ERR_SSL_INVALID_RECORD')

Closing this as more searching seems to indicate that getting reliable TLS or maybe even SSL
on various ESP32 platforms using Micropython could be difficult. Maybe, one has to freeze code.
I read several threads re "heap allocation" and got "lost".