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I can't read my mails and every time i open Thunderbird i get told that my registration failed and i have 3 Options to choose "try again", "enter new password" and "cancel". Doesnt matter ehich one I choose i can't read my mails or receive any and the same message and the same options pop up again.

One of my two outlook email accounts no longer appears in Thunderbird, which says it is authenticated but not connected. This happened suddenly. I can still get the messages by going onto outlook.com. How do I get it back on Thunderbird?

I need help with a problem that has tortured me for weeks. I use debian 13 with plasmakde. I don't know why, but when I connect to a wifi after some time it doesn't work anymore ONLY with Firefox. I can perfectly use any other app which requires internet but firefox. Sometimes it gives me the error "The connection has timed out", sometimes the error "Unable to find the proxy server" (even if I selected no proxy in the network settings). I searched online but I couldn't find anything helpful, so I can only hope to find a solution in here. Thank you very much in advance!

Hi! I hope you are well. It's my first time trying Thunderbird. I have the Linux Mint app. (seems to be the latest version available from the Linux Mint app store)

I attempt to sign into my Outlook.com email address on Thunderbird.

When I type my Outlook email and password and click Done, Thunderbird says configuration found in Mozilla ISP Database and it tries to pop up a browser window. Some website like login.microsoftonline.com is in the URL bar, but the browser window closes immediately without displaying a page.

Thunderbird say authentication failed. Either the entered credentials are incorrect or a separate username is required for logging in."

What do you think about the cause of this issue? Is this possibly an issue with my Outlook account or the Linux Mint version of Thunderbird?

I found a similar issue mentioned from a few years ago:[https://www.reddit.com/r/hyprland/comments/17q16cg/thunderbird_authentication_window_is/ https://www.reddit.com/r/hyprland/comments/17q16cg/thunderbird_authentication_window_is/ ] Where they used Linux and Thunderbird would open and close the Outlook window without giving a chance to login to the Outlook account.

On my computer, I tried: type a yahoo address into Thunderbird and click done and it opens a Yahoo website login window. So Yahoo seems to work, Outlook doesn't. Outlook's login window disappears by itself.

I was wondering if you have any suggestions for me? Is this the wrong place to report bugs (if you think its a bug)? (The Thunderbird app takes me to this place when I click Help > Share Ideas and Feedback.

Thanks so much for your time. :-)

Thunderbird info: Thunderbird for Linux Mint mint-001 - 1.0 140.8.0esr (64-bit) Linux Mint 22.3 - Cinnamon 64-bit

My Thunderbird will not connect to the Comcast/Xfinity email account with the same settings that Outlook connected to and downloaded all my emails and my inbox structure. I believe this is either a battle between Comcast and Thunderbird or a big glitch in this application, My Gmail, Outlook365, work fine in Thunderbird, not Comcast. This started about a week ago. Has anyone found a solution?

bold text When I try to go to my "FIREFOX" it answers me in French of course but here you don't accept to write me in French and so it's very difficult for me ... (could you help me for this of course ???) : "hmm this adress doesn' seem to be valid." Hum, cette adresse ne semble pas valide.

What must I do please ??? [edited from public] @orange.fr

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?

Hi,

OS: Linux Manjaro 6.18.12-1 (Cinnamon 6.6.7) Thunderbird: 147.0.1 Email: google account

Everything worked perfect till I upgraded to version 147.0.1 When after replying or writing new email, hitting the [send] button I always get this error message

"Sending of the message failed. The message could not be sent because the connection to Outgoing server (SMTP) smtp.gmail.com timed out. Try again."

Click [OK] and save the message or messages is dropping them in the 'Drafts' folder. Close Thunderbird and start it again. Then double click the messages in the [Drafts] folder and hit the [Send] button, will send the messages without problem.

Nothing changed to my setup, I only upgraded to 147.0.1. Another weird thing: every-time I start Thunderbird it creates a Thunderbird directory under my home.

Is one connected to the other? Has somebody an idea what's going on/wrong?

Many thanks in advance

I am using the Thunderbird software (140.7.1esr 64-bit) for mail merge purposes on a Windows 11 operating system. However, when I start the mail merge process, it begins initially but then automatically disconnects before completing the task.

Due to this issue, I am unable to complete the mail merge properly. Kindly look into this problem and provide a solution as soon as possible.

Thank you.

For 3 days now I have been unable to connect thunderbird to microsoft outlook. I have all the latest settings checked online with microsoft and it keeps failing... any suggestions on how to overcome this? Thanks

Hi, Since up-date of Thunderbird on 02/25/2026, there is no more links nor update in my google agenda in thunderbird ( 148.0 realesed ). ?? Have you got any solutions? Regards

not connecting to server as of today

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

Hello everyone,

We are currently investigating an issue where browsers are sending HTTP requests with Connection: close in the header during integrated Windows authentication (NTLM authentication) via SAML Service Provider (SP), leading to premature termination of the TCP connection.

This behavior occurs in the middle of the authentication process, preventing the NTLM authentication from completing and subsequently prompting for re-authentication.

We have observed the following browser behaviors:

Chrome and Edge: These browsers function without issues, communicating with Connection: keep-alive. Safari (macOS): Older versions of macOS with Safari exhibit the Connection: close behavior, leading to authentication failure. Newer versions of macOS with Safari work correctly with Connection: keep-alive. Firefox (macOS): Even on the latest versions of macOS, Firefox continues to attach Connection: close, resulting in authentication failure. Upon reviewing logs, we've identified that various browsers attach the Connection: close header during the NTLMSSP_NEGOTIATE request in the NTLM authentication sequence. Although this happens in an environment with a load balancer, we have confirmed that the load balancer is not modifying the header; rather, the client (browser) is adding it.

We would appreciate your insights into the conditions under which Firefox attaches Connection: close to HTTP requests, especially considering the differences across macOS versions and other browsers, addressing the following points:

Are there any known conditions or past cases where Firefox outputs Connection: close in an NTLM authentication environment via SAML SP? Given that older Safari versions show similar behavior, we are also considering if there's a common factor depending on NTLM authentication and browser version. What are the general heuristics, logic, or triggers for a browser to decide to "close" a connection or to attach Connection: close? We are particularly interested in cases that occur mid-authentication process. Could specific configurations (e.g., the combination of SAML and NTLM authentication, or the presence of an intermediate proxy/load balancer) potentially influence Firefox's Connection: close behavior? Are there any additional logs or debugging information we should collect from the Firefox client side to further pinpoint this issue? Any guidance or suggestions you could provide to help us resolve this problem would be greatly appreciated.

Thank you.

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".

I have a new laptop with windows 11 (previously had a computer with windows 10) I got Thurderbird onto my new laptop however when I try to get in emails it keeps asking me for a new password. I keep entering the password for my provider but it does not remember it or does not accept itl It says its trying to connect to server but never does. then after a while it says it timed out. Is there another password I should be using?