Do the Yahoo accounts apply OAuth2 authentication?

https://support.mozilla.org/en-US/kb/thunderbird-and-yahoo#w_important-changes-to-authentication-method-notice

Thanks. Yahoo support website says that Thunderbird does not support OAuth2 and advised me to use a secure mail key to sign in from TB. I did that and am now able to send and receive messages from TB. But I now have two TB inboxes, one of which I can't access. I assume that the one I can't access is the inbox for the TB account that I removed when I was trying to get TB to connect with Yahoo. I was able to download all of the messages from my Yahoo inbox into the new TB inbox. The problem is I have just discovered that most of my old messages are missing from the Yahoo server. I only have messages in my Yahoo inbox going back to Nov 7. I think they should still be in TB somewhere. I would like to know how to retrieve the old messages from wherever TB has stored them and move them into my new inbox. There is some pretty important stuff in there.

Yahoo website is out of date. TB has supported OAuth2 for Yahoo POP and IMAP accounts for several months. If your account is IMAP, all mail is stored on the server. If it's POP, some mail may be on the server and some in the TB profile folder, depending on how many and what kinds of accounts you have added and removed. Help/Troubleshooting, Profile Folder, Open Profile. POP accounts are in the Mail subfolder, IMAP accounts in the ImapMail subfolder.

Thanks. I did try to tell TB to use OAuth2 but when I went into manual configuration OAuth was not an option in any of the drop down menus. So I ended up using the settings that TB determined when I set up my new account but instead of my Yahoo password I used my Yahoo secure mail key. And it worked. I am afraid to change any settings now because it basically took me all day yesterday to find the solution that finally worked. My problems would be solved if it weren't for all these missing emails from my old inbox.

I used Help, Troubleshoot and found a folder in Profiles called Mail that has the following subfolders: inbound.att.net Local Folders pop.sbcglobal.net

All of which show that they have been modified today. I assume that these contain at least some of my old messages. How to I restore those to my TB inbox?

There is a folder called imap.mail.yahoo.com but the files in there are very small, only about 2K so I don't think there is much to be retrieved from that folder.

I did try to use OAuth when setting up my new TB account but I could not find that option among the various drop down menus when configuring the settings. So I followed the instructions from the Yahoo website and set up my TB account using the settings that TB determined but using my Yahoo secure mail key instead of my Yahoo password. It worked and I am reluctant to change any settings at this point - it took me so long to find the solution that finally worked.

I went to Help, Troubleshoot and opened the Profiles folder and found a folder named Mail that contained subfolders that look like they contain at least some of my old messages. How do I restore those to my TB mailbox?

Close TB, open a subfolder of Mail that isn't the storage location for the current POP account, look for the mbox files, the large ones with no extension, named after folders, such as Inbox, and copy them to Mail/Local Folders, renaming if necessary. Restart TB and find the folders under Local Folders in the Folder Pane.

Thanks! I will try that. Hope I don't screw anything up.