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I sent a request for help and got this response:

"Well you might start by actually advising what the error is. We are at this point left to guess what "When launching Thunderbird, I get a pop-up saying Server "outlook.office365.com" reported en error" means and I can assure you it is not much to base a guess on. What is the message verbatim?"

You missed the point entirely! The point is that there NO ERROR CODE REPORTED, only the cryptic information I sent earlier. Further, if I knew the error code, I could fix it myself. The question is whether there is some kind of a log file kept in Thunderbird that may shed some light on the problem. Hopefully, now you understand the problem and can respond in a more meaningful and professional manner.

Some additional information: (a) sometimes email does not send, (b) I have already reinstalled T-Bird with with the mystery error continuing, (c) no errors were reported during installation. If there is no log file that T-Bird keeps and if you have no way of helping me track this down, T-Bird has ceased to be a practical alternative to Outlook.

I periodically get a T-bird notification "Server imap.gmail.com has disconnected". If I wait for 30 sec to a minute, the connection reconnects and everything is fine, until it does it again. If it disconnects in the middle of sending a message, the send action will freeze and perhaps, time-out if the disconnect time is too long. Any ideas about this periodic disconnection? I'm using version 128.9.2esr (32 bit) with Win10 pro.

Thanks, Tom Hayes

not connecting to server as of today

Login to server mail.tds.net with username [edited]@tellink.net failed.

Hi I have switched to Mozilla from Chrome as I can’t update latest OS for my Mac. I can only browse internet intermittently and just want to ask if there are any settings I need to change on Firefox? Thanks Aidan

Thunderbird sagt, E-Mail-Adresse, Passwort oder Konfiguration seien falsch, Anmeldung am Server nicht möglich, obwohl ich mich über Mozilla Firefox auf dem Vodafone-Server einloggen kann. Was kann ich machen?

Using Firefox as my browser, I have over the last few days been unable to maintain a connection with the internet.

You will please excuse me as I am a 70 year old with limited understanding of the interaction of the internet and its terminology.

A couple of things you may need to know to offer me advise I just received a refurbished Dell laptop with windows 11. I'm using firefox as the browser comcast xfinity is my ISP I subscribe to NordVPN and NordPass

I am having a problem maintaining a connection to firefox.

I can look on the taskbar and see that I am connected via Comcast and the NordVPN and yet I will have displays of "you are not connected to the internet" or similar wording. If I need to include that, at these times, I look at the task bar and I confirm that I am connected.

In addition to this Windows 11 laptop, I have two active android phones. My Gmail, last I checked on the laptop was displaying vividly inaccurate time stamps to incoming emails. My phones however show the emails with accurate timestamps. (A difference of 4 to 6 hours like EST New York to middle of the Pacific Ocean)

I do have photos of these events, screenshots of sorts... but they're on the phone. I'm currently using the firefox browser to offer this post/question, but I sit in anticipation of it acting erratically. Finally I have downloaded a different browser to use while the firefox issue is being trouble shot.

Rather than add more possibly irrelevant information, I'll send now and let the community ask me questions.

Al R

Quand l'envoie une PJ avec un compte qui a smtp.free.fr, j'ai le blocage "L’envoi du message a échoué. Le message n’a pas pu être envoyé car la connexion au serveur sortant (SMTP) smtp.free.fr a expiré. Veuillez essayer à nouveau." Si je l'envoie avec un compte qui a smtp.sfr.fr, je n'ai pas de problème ! Je suis en Thunferbird 146.0.1 (64 bits) sur Windows 10. Merci de votre aide.

the msg returned

Hmm. We’re having trouble finding that site.

We can’t connect to the server at marvelsearch.com.

If you entered the right address, you can:

   Try again later
   Check your network connection
   Check that Firefox Developer Edition has permission to access the web (you might be connected but behind a firewall)

i am using a local dnsserver and firefox is connected to it. is this the reason? if so how can i disable this? other firefox features are working beautifully.

After the 146.0.1 update (installed on December 10th, 2025, OS: Windows 11 25H2), when Thunderbird tries syncing a college email account (email format: first.last@schoolname.schoolabbreviation.edu) I get the following error message popup as a Windows notification: "Server outlook.office365.com responded with an error." When clicking on the error message, it doesn't provide any additional information (no error code or detailed message of what's going on).

Below is the troubleshooting steps I have already tried.

• Restarted computer
• Repaired Thunderbird installation
• Tested connection to server under Account Settings>Server Settings. Shows successful connection.
• Cleared Thunderbird startup cache

Since the account still seems to send and receive emails just fine, I haven't tried removing/readding the account or doing an uninstall/reinstall of Thunderbird.

Any suggestions on where I can find details of what is causing this error and how to fix it? If I need to provide more troubleshooting information, please let me know.

I recently installed Thunderbird on Debian 13 and I wanted to use it as my default email client. I tried to connect it to my university account and even though I'm confident the credentials are correct I'm getting the "Unable to log in at server" error. I also want to note that I'm getting the success message saying "Configuration found at email provider".