try using outlook.office365.com and smtp.office365.com, or just let Thunderbird do the setup. Did you have messages in the other folders? Is this POP or IMAP? Report back after adjusting server names.

Tried using the defaults initially and then tried specifying the servers. In both cases I successfully set up a yahoo account with sub folders okay.

It is a a shame you don't answer the questions asked of you.

Did you have messages in the other folders? Is this POP or IMAP? Report back after adjusting server names.

That information is relevant.

Tried using the defaults initially and then tried specifying the servers. In both cases I successfully set up a yahoo account with sub folders okay.

This information is not of any relevance at all other than to say your yahoo account is working.

A base inbox is indicative of one of two things. David asked you if you were configuring your account as IMAP or POP for a reason.

1. POP accounts only have an inbox, so by selecting POP in the account setup you can ensure you get no other folders.
2. A stand alone inbox can also be indicative of a failed IMAP account. In that Thunderbird has never actually managed to log into the mail account using the credentials you provided. This is usually apparent in the new account setup with a yellow banner saying that a connection could not be established. Clicking for a manual setup from that point will create a non functioning account with only an inbox.

So perhaps with some answers from you, so folk are not guessing about the what you did or why. Could you confirm you are setting up an IMAP account, using the defaults provided by Thunderbird. Which it looks on the internet to download from here https://autoconfig.thunderbird.net/v1.1/hotmail.com and will advise you that it found settings for hotmail in the ISPDB

Then there is the issue that oauth setups (Which both Yahoo and Homail are) need to to have cookies enabled. You got Yahoo to work, so I am not really looking at general oauth failure causes, but mention this one as security software has a rather ugly habit of disabling them without consultation. So check the Thunderbird settings for cookies

In bug 1978361 I see it suggested that setting mailnews.oauth.usePrivateBrowser to true in the Config Editor is a workaround for retained information in the case of Yahoo accounts and ATT. Perhaps try it with this and see if a previous oauth cookie is at issue here with Microsoft accounts.

As I said originally I set up Thunderbird 140.3.1 using the defaults, created two accounts (for testing purposes, both these accounts work okay in other email clients, standard default settings for both). Yahoo account, created folders and could send an receive emails. Outlook only created an Inbox.

Uninstalled Thunderbird and installed 140.3.0, unticked the Account Hub experiment, manually set the input server to imap-mail.outlook.com, SSL and Oath2, output server to smtp-mail.outlook.com, Oath2 and STARTTLS. Yahoo account created okay able to end and receive emails. Outlook only created an Inbox.

On startup : Thunderbird also now generated a truncated message "The currrent operation on Inbox did not succeed. The mail server for account responded: User is authenticated but..<truncation>

Does anyone know what the the rest of the message is please !

This from AI: The error "User is authenticated but not connected" typically indicates that while your login credentials are correct, there is a problem with the connection to the mail server. This could be due to server issues, network problems, or incorrect settings in your email client.