Have you typed the outgoing server name in your server settings the way it appears in the subject of your post or the way it appears in the error message you quoted? Because they're not the same and you may have made the same mistake when configuring the outgoing server in Thunderbird… :)

I wish it were that simple. ;-)

An update to T-bird came out a couple of days ago. Since, I've received several popups to log in to Google from my various email addresses. I have 10 gmail addresses in my Thunderbird client. In sending test messages to myself, only 3 of those accounts send outgoing mail. The other accountss give a couple of messages:

Login to server smtp.gmail.com with username xxxxx@gmail.com failed options are retry, enter new password, cancel same message comes up if I select enter new password (no opportunity to enter a new password)

and then

sending of the message failed Unable to authenticate to Outgoing server (SMTP) smtp.gmail.com. Please check the password and verify the 'Authentication Method' in 'Account settings | Outgoing server (SMTP)'

I haven't changed any stored passwords or outgoing server settings. When I check the outgoing server, every account (both the 3 that send mail and the 7 that don't) shows Google Mail - smtp.gmail.com as the 'Outgoing Server (SMTP)'

And when I click on Edit SMTP server, I see port 465 (default), connection security SSL/TLS, authentication method OAuth2 and the account's user name.

I'm at a loss regarding what else to check/change/do.

Thanks for your help.

The following article would explain what's happening if you were being asked to sign in to Google to authorise Thunderbird. What's strange is that, instead of that, you're being asked to authenticate as if you had to do that with username and password instead of using OAuth2. But take a look at the article anyway, just in case:

https://support.mozilla.org/kb/automatic-conversion-google-mail-accounts-oauth20

In particular, make sure you have cookies and javascript enabled, as described there.

I really appreciate you help in this puzzlement

Now 5 of the 10 accounts can send email. All are listed in the "saved logins" with OAuth2 authentication. I've deleted imap.gmail.com and smtp.gmail.com saved logins for the 5 accounts that aren't sending.

javascript and cookie settings are as specified in the referenced article

One curiousity: when trying to send from one of my accounts, the

Login to server smtp.gmail.com with username xxxxx@gmail.com failed

popup specifies a DIFFERENT email account, rather than the one from which I'm trying to send.

Should I just delete all of the saved logins and add them back manually? Anything else.

You may have multiple outgoing server settings, stored independently of any (incoming) account settings, then associate each account with the outgoing server you want to use with that account. Maybe the problem is that you don't have each of the accounts configured to use the right outgoing server?

It's not clear to me whether you're familiarised with the separate Outgoing Server (SMTP) settings pane I'm talking about. You can see it in the following article if you're not:

https://support.mozilla.org/kb/cannot-send-messages

Add new outgoing server settings there for any account that doesn't already have one, then make sure each account is associated with the right outgoing server settings in the main pane of each of the account settings.

I think the problem is solved. I had 11 gmail accounts synched to Thunderbird, and not 10. Apparently, Google only allows synch to 10 accounts. When I deleted one of the accounts from Thunderbird, all the other accounts logged in to Google and all can now send mail.

Thanks.