In 'Account Settings' > 'Server Settings' for each account there is 'Local directory:' bottom right

Does each account point to the correct location? eg: original yahoo

• C:\Users\Username\AppData\Roaming\Thunderbird\Profiles\xxxxxxxx.default\ImapMail\imap.mail.yahoo-1.com

New yahoo account

• C:\Users\Username\AppData\Roaming\Thunderbird\Profiles\xxxxxxxx.default\ImapMail\imap.mail.yahoo-2.com

Please check to see what is stored in the Passwords section. Menu app icon > Options > Options > Security > 'Passwords' tab click on 'Saved Passwords' Click on 'Show Passwords'

You will have two per account one is incoming and one smtp outgoing. The 'site' column may show identical information for both Look at the 'Username' and the 'Password'

Do you see anything that looks wrong?

DING DING DING!!! I think we have a winner, Toad Hall. In terms of the "\imap.mail.yahoo-2.com" structure: yes each of them is unique. My Profile has been located on a different drive (D:) so the path is different but it has always worked fine.

BUT you put your cursor right on the problem with the password settings. I did not know one could see the passwords this way. The OATH passwords for both accounts match but that password is not the same as the uniques passwords used for logging each email into Yahoo using a password manager and through a browser.

Also the IMAP password for the original email and the SMTP password for the new email are the same and that password matches the Yahoo login for the original. Lastly, there is no SMTP password for the original email.

I am curious where these passwords originated since I did not assign them? Any reading material on this? I seem to also recall (may be different issue) that Yahoo suggested a less rigorous/secure setting in Yahoo in case of a login issue. Could be related? I guess I think the solution might be to remove each conflicting account from Thunderbird and close it. Then login to each account via a browser and change the password and then start Thunderbird and wait for a prompt for the password? I'm not sure what would happen.

Definitely open to your direction/suggestions. Meanwhile, great help!!

re:Also the IMAP password for the original email and the SMTP password for the new email are the same and that password matches the Yahoo login for the original.

Normally you would say this is Not correct. But, it makes me wonder what smtp you are using for each yahoo account as you did mention: that in the section that displays the account names info that the last column "Default" is false for the original Yahoo account and I think this pertains to which identity is the default and this address is the ONLY one of the Yahoo addresses that has an alternate send SMTP identity.

It sounds like before you added the latest yahoo email address/mail account called imap.mail.yahoo-2.com, you had set up the original yahoo account to have an additional identity. Did you set up an additional identity for original yahoo account which happens to be the same email address as the last yahoo account you tried to add as a mail account ?

If yes, then I would advise you remove that additional identity because you no longer need it as you are trying to create an mail account of same name.

• access the Account Settings for original yahoo account.
• Click on 'Manage identities' button
• Make sure the identity for the mail account is the same email address as the account and set as default
• Select additional identity that is not the same as mail account name and click on Delete.
• click on Close

Then make sure the original yahoo mail account is using it's own smtp server.

In 'Account Settings' window

• Bottom of left pane click on 'Outgoing Server (SMTP).

There should be 3 smtp outgoing servers for the three yahoo accounts. You need to be able to differentiate between them.

• Select first one and click on Edit

The User Name shown will be the email address.

• 'Description' : This is very useful. Please type something more meaningful in the Description such as the email address that you see in the User Name.
• click on OK.

Then repeat same action for the other yahoo smtp servers. If you only have two, then you may need to create the third for which ever 'User Name'/mail account does not have it's own smtp server.

Now make sure each account is using their own smtp server.

• Select the mail account name in left pane and bottom right it will say 'Outgoing Server SMTP'.

You will see how useful the Description will be. You need to use the one that has the same email address as the account.

• Click on the drop down to select the correct one for the account.

When all yahoo mail accounts are correctly using their own outgoing server,

• click on OK to close the Account Settings window.

Now access the saved passwords area. In the saved passwords location this is what you should see. The lines that starts with imap:// and the smtp:// will have a username that is the same as the email address and a unique password that is the same as the one you use to logon via a browser for that email address

You say : the IMAP password for the original email and the SMTP password for the new email are the same It is possible to edit the passwords. right click on SMTP line and select 'Edit Password'. Make sure all the imap:// and smpt:// lines have a user name with the correct password for that email address.

re:The OATH passwords for both accounts match but that password is not the same as the uniques passwords used for logging each email into Yahoo using a password manager and through a browser. Oauth passwords will be different to the normal password. the oauth:// line uses what they call a token, loads of letters and numbers in a long string. This is created by yahoo. When Thunderbird auto connects to server it will use that oauth token both for receiving and sending. But, it does seem odd that both tokens are the same for both accounts.

Select the one that has username for newly added email address. click on 'Remove'

click on 'Close'

When you set up a gmail account to use Oauth, you get directed to logon to confirm you really are you and to allow thunderbird to connect to server. I presume this is the same for yahoo. This is the point where the token is created. So you would expect the same sort of process being used by yahoo.

Exit Thunderbird and all the changes will get saved, so wait a few moments for background processes to complete.

Start Thunderbird.

When the newest account tries to access server you may get prompted to enter login details, so please make sure you enter the correct username/email address and password and a new oauth token should get created.

WOW! A lot to absorb here Toad-Hall. I will tackle all of this in an orderly fashion sometime today. For now, I can say that the additional identity for the original email does NOT match the newer Yahoo address in any way.

I'll get to this and let you know the results as soon as I can.

Thank you!

Hello Toad-Hall. My apology for this slow reply.

I eliminated the secondary identity that was associated with the original email and restarted everything. The "false" setting in the Default column of the troubleshooting listing changed to "true" for the original email address. I'll be interested to see what happens when/if I add an identity to this. But I think this is not part of the issue we've been discussing.

I can observe that all the Yahoo accounts have the exact same SMTP. This was the case for all the Yahoo accounts even before the issue with the newer email account receiving the original account's messages occurred.

I did as you suggested and changed the SMTP description for each of the accounts. It did help distinguish things separately. But it did not change the details that I could observe about the SMTP settings. Everything remained unchanged and the SMTP was still smtp://smtp.mail.com .

Since the other Yahoo accounts were working fine I disregarded that there were not unique SMTPs.

So I then looked at changing passwords (in the Tools\Options\Show Passwords) listing. I just wasn't sure what to do with the passwords since the original email didn't have an SMTP setting or password in the first place and the IMAP password for the original email and the SMTP password for the new email were the same and the passwords matched so I really didn't know what to do. It occurred to me that the issue might not be with Thunderbird but maybe with Yahoo since Yahoo determined the OAUTH token settings maybe it had also confused the imap settings. I removed the new email account from Thunderbird, choosing to delete the messages and then closed Thunderbird. I had done some looking around in the Profile and found a PREFS-2.JS file that had the newer email account name in it (other PREFS-nn.js files had the other Yahoo accounts in them) so I killed this file also.

Then I double-checked the Yahoo accounts' logins by logging in/out of each one on FF. Everything worked just fine. No crossover emails etc. No dupe passwords. And Thunderbird was working fine with the removal of the newer account.

Then I set about adding the new email to Thunderbird again. I used File\New\Existing Email Account and no matter what I tried, manual or default settings, I kept getting an error that "incoming mail server already exists". I tried various changes in server name, port #, authentication method, and connection security but nothing seemed to work. Same error repeatedly.

So I did some further exploring and experimenting. I logged into the newer email account on FF. In Thunderbird I right-clicked on Local Folders, chose "Set up an account:", Email and used the panel to sign-in using the newer Yahoo email login. This prompted me with a Yahoo screen about signing in with a third-party and I then entered login info and voilá the account was added to Thunderbird. The settings were exactly what I was entering via manual and default entry of server name, port #, authentication method, and connection security, etc., that I had used before when trying to add the account back in.

Except this time everything worked fine. I was able to replicate this result by creating yet another new Yahoo email and bringing it into Thunderbird.

I don't understand why this worked or quite how it worked. It does seem that Yahoo acted to establish authentication passwords that are unique for each email account and that neither Thunderbird or Yahoo mixed things up. No passwords are duplicated across email accounts. There is a hodge-podge of results of email accounts that have various number of passwords: 4 accounts have passwords for OAUTH/IMAP/SMTP, 1 account that has only OAUTH/IMAP, 1 Account (the newer email that started this whole issue) that has only OAUTH, and 1 account that has OAUTH/IMAP/SMTP + chrome://gContactSync/oauth (a gmail account but another gmail account does not have this gContacts entry but I'm sure that is because I do not have contacts, per se, for the other gmail).

I want to thank you greatly for your help. Your insight and questions have led me to a resolution. To quote an old friend, "I don't understand all that I know."

Thanks!