have you checked the credentials that Thunderbird is using? Like the password. Google require oauth2.0 authentication and that should have been corrected last year when you had issues. But Google wrote to me this week telling me I must use two factor authentication. I am not sure how I am going to dump that requirement. I just might have to move to another mail provider like GMX.

Have you tried to log into your gmail account using a browser recently? Google have a habit of blocking mail if they have something to tell you until you log in using a browser.

Thanks for the thoughts, Matt, but this doesn't do the job. I consistently use two accounts. As a freelance journalist, my handle is “eeyore944.” My personal account handle is “eeyorehome9.” Both are @gmail.com.

Eeyore944 appears to be working in part; as of last weekend, that account had received 101 emails since 6:00 a.m., Dec. 12, which is a normal incoming volume, but I can’t send out with Thunderbird from that account.

Eeyorehome9 is not so clear or simple. The flow of messages addressed to that account since 12:52 a.m., Dec. 12, has been badly disrupted. On Dec. 15, I received seven emails there, but with that exception, eeyorehome9 has received between one and three each day since Dec. 12. Incoming daily volume for that account normally is in the dozens.

When I try to send from eeyorehome9, either in reply or with an original message, the client responds with messages like these: Sending of the message failed. Unable to authenticate to Outgoing server (SMTP) smtp.googlemail.com. Please check the password and verify the 'Authentication method' in 'Account Settings | Outgoing server (SMTP)'. The STAT command did not succeed. Error getting message number and sizes. Mail server pop.gmail.com responded: [AUTH] invalid credentials.

Somehow during this period, my Gmail login became corrupted and my password didn’t work. Within a day or two, Gmail corrected that, so I am able to communicate via original Gmail, but not using Thunderbird.

As for Thunderbird's credentials, my password is created by and saved in 1Password, which I have used since 2019, and my TB password has remained unchanged since many years before then.

Like you, I am reluctant to use two-factor authentication. But I haven't been told I require it.

Would it be possible to overcome this problem by reinstalling Thunderbird over the existing app? I think there is a way to do that without loss of existing messages and data, but don't know whether it would solve the problem.

My browser is Firefox, but I don't know how to login from it.

Again, Matt, thanks for the input. Have you any more ideas?

I would suggest that you first up start using the Google server names that have been in use since gmail came out of Beta.

Pop https://support.google.com/mail/answer/7104828?hl=en IMAP is server imap.gmail.com Port 993 with SSL/TLS connection security (for some reason I can't find those setting on the gmail web site like I can for POP

All Authentication methods for Gmail are to be set to OAuth2 and I would suggest you dump your password manager for Thunderbird as oauth uses cookies and tokens stored in the password manager and to be honest I have no idea how those would work in a password manager. The OAuth process does not use traditional passwords, but token issued in the initial authorization process using a Thunderbird web browser, and renewed by the server as required, until such times as it decides the whole authentication process needs to be gone through again. I find Google to be about once a year.

Thanks again, Matt. I'm certainly willing to try your proposed solution, but first I need to clarify: Are you saying I may need to abandon Thunderbird to solve this problem? Or is gmail the problem, and I can solve it by using another email? Are my options really so limited? Has Mozilla rolled over and accepted Google's fiat without protest? That doesn't sound like the Mozilla I have trusted for years and made contributions to. Please, help me understand. I see the wisdom of two-factor authentication, and I can see how a requirement to adopt it for my login to Thunderbird or any other client would make a serious difference in my ability to use it. I have seen some discussion of passkeys replacing passwords. Would they provide security equivalent to two-factor auth? If so, could I bypass gmail?

I believe Matt is suggesting to stop with 1Password and let Thunderbird administer that. Also, to change account to use smtp.gmail.com and use Oauth2. I defer to Matt about two-factor auth, but I use gmail and have received no notice on that. On original setup, Google prompts for email address and password and then places a unique for you in Thunderbird, never needed again.

I defer to Matt about two-factor auth, but I use gmail and have received no notice on that.

So far, it has only appeared as a notification on my phone. I hope I can sidestep it somehow as I pop in and out of gmail/workspace frequently when on this site checking URL's and settings. I do not want to be "helped" by stopping every little while to get a code from the phone.