Wow major thanks for digging this up @Varstahl. I'll do some local experiments when I get time but given I have a mix of OAuth and normal password accounts this is likely the problem. This is quite an annoying bug so thanks again for narrowing it down.

To all people who have this not remembering password during session....AS A TEST: Could those effected by this issue, access the Account Settings > Server Settings for accounts that use OAuth and disable the option / uncheck the checkbox 'Check for new messages every X minutes' Then restart Thunderbird and enter passwords as normal. Observe what occurs regarding getting prompts for password. Please report back with your observations and results.

It would help try to identify what is triggering this problem, but we need all those effected to test this. Please help by providing information.

@Toad-Hall as I said in my previous comment I did exactly that, and as long as OAuth2 doesn't fetch/send e-Mails, the passwords are not asked again, ever. Ran it for the past 9 days straight, never popped up.

@Toad-Hall as I said in my previous comment I did exactly that, and as long as OAuth2 doesn't fetch/send e-Mails, the passwords are not asked again, ever. Ran it for the past 9 days straight, never popped up.

I noticed your valuable contribution and findings, hence why I asked if everyone else discovered the same issue and it would be useful to know if they discovered after gradually switching that option back on for one account at a time, if it was a yahoo server/account causing the problem. It is really a question of getting a load of feedback for the developers to help them get to the bottom of this annoying problem.

So for others reading this, please respond with your results to see if Varstahl's testing is reproducable.

@Toad-Hall I've been running with this setup (unchecking the "Check for new messages every X minutes" checkbox on all my OAuth accounts) this past week after Varstahl's update. I periodically manually fetch messages for these OAuth accounts and seem to have similar results.

A few things - at least for me, it doesn't forget the password immediately after fetching the mail for an OAuth account, it seems to have some time in between, but definitely seems related since I can go all day without checking those accounts and not typing the password, but then within a fairly short (I think less than half hour) period of fetching mail for that account it does seem to forget the password again.

Also, it doesn't seem to happen with my gmail OAuth accounts, only yahoo. If I fetch from a gmail OAuth account, it doesn't seem to forget the password for quite a long while (if ever) whereas if I fetch from yahoo, that's when it forgets within ~30 minutes or less. However, since the forgetting effect isn't immediate, it's a little harder to tell for sure what's going on - perhaps it needs the combination of gmail + yahoo to trigger the bug, or maybe it really is just yahoo by itself.

I'll keep observing and try to update if I find anything else relevant (or if there's any further specific tests you want me to do let me know).

I have had the same problem since creating a yahoo imap/oauth2 account almost a year ago. I do not automatically monitor my oath2 account so it doesn't bother me much. I also have 2 pop3 accounts which get automatically checked every 15 minutes. Whenever I manually select my yahoo account and it goes through its authorization process, the pop3 accounts stop auto checking, and if I "get mail" on them, I have to reenter the password. If I use the pop3 accounts IMMEDIATELY after using the imap account I have the same problem without any delay, as taz is experiencing. It is as if thunderbird is discarding all authentication information for POP/SSL-TLS accounts while handling an IMAP/Oauth2 account.

This is a reported bug and is being investigated.