Me too.. after several hours, I found that when looking at account settings, scroll all the way down until you see "outgoing server (SMTP) at the bottom. There you can add, delete, or change them to your heart's content.
I added my own and used the "description" area to give them clearer names and when I finished selecting them and modifying them, lo and behold, they "stuck" and didn't get changed anymore.
I figured it out, thanks!
test...
I don't think you have started at the right place. When you are looking at the TOOLS/account settings, see there is a scroll bar on the left. You are looking for "Outgoing server (SMTP)" and it may not show up until you scroll all the way to the bottom. Also what is working for me is for all the SMTP server settings, CONNECTION SECURITY is set to SSL/TLS and the port number is 465. Plus OAuth2 of course.
