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I have been using Firefox on my iPhone for years without problems. But for about a week now if I’m on data it can’t load any websites, a message appears saying it cannot connect to server. It works fine when I’m on WiFi.

Error code: PR_CONNECT_RESET_ERROR

   The page you are trying to view cannot be shown because the authenticity of the received data could not be verified.
   Please contact the website owners to inform them of this problem.

Afterward no mail is being received from any of the providers, everything is stopped at last time I connected before the error, i.e. 7/9/2026

I have a similar problem to others reporting a connection time-out. But the circumstances now seem different. It is getting worse. First thing today, I noticed that Thunderbird emails (current/up-to-date version) were taking several minutes to finish sending. After sending 3 successfully, but slowly, all further emails failed, as per image attached. My wife's computer, using the same email provider, etc, was working okay. I checked and compared the account setting, and they were slightly different (no idea why) so I altered mine to match the other PC. That didn't make any difference anyway. Then (a few hours later) my wife's PC started having the same problems as mine, as if it's a spreading disease. Could it be a virus? Thanks.

Each time I attempt to login w/ T-Bird, google mail gives me this message:

400. That’s an error.

The server cannot process the request because it is malformed. It should not be retried. That’s all we know.

Please see attached image of the problem.

I have tried looking on Google for ideas but have not found anything on this or how to fix. Hope someone can please help would be amazing!

Google -

400. That's an error

The server cannot process the request because it is malformed. It should be retied. That's all we know.

I have been using Thunderbird for many years. I have 4 accounts that have all been set up and working fine. This morning the 2 yahoo.com accounts stopped working. I logged in to the impacted accounts using a web browser and password just fine. I then updated Thunderbird to 116.0 to see if that would fix the problem, but it did not. The outlook and gmail accounts are working fine, for now.

When Thunderbird attempts to download mail for the yahoo accounts, I get a large pop-up window with "Edge: Too Many Requests". The pop-up window is blank except for that error message. I get the small pop-up with the Authentication Failure message. Sometimes I get Retry, Enter Password or Cancel. But I never see a window that will allow me to enter my password.

I can send/receive mail from the accounts while logged in via a browser but authentication fails within Thunderbird.

I use Thunderbird when Postbox acquired another. I am using 2 computers - desktop, old (10+ years), still Windows 10, and 2 two emails; new laptop (traveling), Windows 11. I download Thunderbird and set up my accounts - gmail.com and twc.com. Troubles with gmail.com, but finally I set up. However, I can't set up twc.com. I like twc.com-- no reason. (Time Warner Cable (twc) bought Spectrum. ) I can login twc.com webmail. Not Thunderbird. I looked carefully set up, Thunderbird searched, found "Host: mobile.charter.net" (Huh?, , continue, enter my password - "Error: ---". I removed VPN Windows 11, no difference. (Curios, my laptop and Firefox, my bank rejected connection. My desktop and Firefox still connects! I dread the day must update.)

I am look forward yours reply. (Maybe Spectrum is searching to dump twc.com.) Jeremy Fields P.S. I wrote with my desktop - windows 10 -, my new laptop (windows 11) is problems

The system was working fine. The next day, when starting Thunderbird (TB, the status line shows logging in to server but loops; no errors or messages, Thunderbird is 'locked out' spinning. I see the normal INBOX page, but logging in never completes. NO CHANGES were made to TB accounts or settings. I have re-installed TB, re-booted, but no change. I cannot check/change any of the accounts or do any further 'debugging' because TB is spinning. The server login is fine because Webmail can be used. Internet connection is fine, because browser works. 1. How can I stop TB from trying to login at start up? 2. What could/would cause this behaviour?

Any suggestions much appreciated.

I asked a question last night about whether or not Firefox had an IP Address. Sounded silly, but I was dealing with an unfamiliar IP. I did eventually find apps that locate IP Addresses. Problem solved . Just want to thank James for taking the time to respond to my question.

Does Firefox VPN not work with DNS over HTTPS set to Max Protection, and when using a custom provider?

With the VPN on and DNS over HTTPS set to Max Protection set to custom provider, no pages will load and I get an error screen/can't connect to proxy screen.

I have been having troubles logging in with my Microsoft email account on Thunderbird (hotmail). When I fill in the name and email address, a pop-up appears with the OAuth2 authentication but the only thing that ever appears in this pop is the message "Unable to connect" with some additional possible explanations.

I have looked online a lot for solution but nothing seems to work. I have cleared the cache, removed all mentions of the email account (it was working before until I added a passkey to the account).

Other reasons I have seen is that the request might be intercepted by certain problems like Apache or Nginx etc. I am running an instance of Nginx on my home server, which is a different device. But I have temporarily turned it completely off but it did not change the situation. The same story with and instance of PiHole, it turns on my homeserver which is a different device and also had to turned off.

The machine I am running Thunderbird on is a Windows machine. I have also tried booting into safe mode with networking but also that did not do anything.

I have tried copying the url on the top of the pop-up window and pasted into several web-browsers. There is does load and I can select the correct passkey to login. But the data that comes back from it is not being given to Thunderbird of course so it does nothing. But the fact that it is able to load outside of Thunderbird makes me think it is a problem on the side of Thunderbird.

Could you perhaps help me set up my email on Thunderbird?

I'm a beta update channel user, so this may not reflect what 'normal' users are seeing. I use Firefox in Linux, debian v13, so normal people that are using Windows or MacOS also might not see the changes I'm asking about? -- I have no way of knowing.

Anyway: in FF v152.0b6, the "Connection Settings" area seems to have disappeared entirely from the settings menu. I used this area of the settings frequently.

The ability to set proxy still exists in the about:config settings area. In the future, will about:config be the standard place to go for people that want to manually set (or toggle) an http/https proxy?

Thanks for reading, and thanks to all the Volunteers who make this place and Mozilla software function. I use your stuff all day, every day, and my life is better because of it.

As of a few days ago, I have the latest thunderbird installed and can't say when this began happening, but despite it working for years with two gmail accounts, neither gmail account will now sync / connect and it has authorization issues.

I've then tried running thunderbird in a sandbox / uninstalling / reinstalling / deleting the user profile / registry entries, you name it...when setting up a gmail account in thunderbird, an error of "Authentication error. Unable to log in at server. Probably wrong configuration, username or password." come up, despite the password being verified as correct.

If I manually setup gmail using the gmail settings, of imap.gmail.com / port 993 and SSL / TLS and Oauth2, and do a test, I'm met with "Connection to server.imap.gmail.com:993 failed"

Nothing has changed on my computer in the time leading up to this not working. No windows updates performed...no changes to the firewall etc. You name it. I've checked it all.

Strange! Any ideas? Thanks!

Recently tried to switch back to using Daily, but now I get authentication errors each time I start the program. It's always the following three errors in sequence: Authentication failure while connecting to server imap.gmail.com. The certificate for imap.gmail.com does not come from a trusted source. Non-overridable TLS error occurred. Handshake error or probably the TLS version or certificate used by server imap.gmail.com is incompatible.

I've tried getting rid of all of my saved passwords and even completely getting rid of the account and re-adding it. I've also tried completely disabling my VPN's service in Windows to see if that was somehow affecting it, but nothing.