Thunderbird Community Forum

I've been using TB for years. Recently, I uninstalled it to try other mail clients. I decided to get TB working again but I'm incredibly frustrated that I'm unable to get an outlook.com account and my nexamortgage.com account working. The NEXA account is google based and is usually quite easy. I also have a Keller Williams account that is also Google based and that worked fine on TB just before I tried to setup my NEXA account. I have tried to enter both manually and have tried multiple different IMAP, SMTP Port settings and Server settings, but nothing is working.

Hello - When I logged into my email this moring a vast majority of my emails from previous days and in my filed emails are gone. Is there a way to get them back? Not sure what could have happened. Any assistance is appreciated!!! Thank you.

I'm dealing with a properly updated 'bird: 140.5.0 (32-bit) running on an equally updated Windows 10 desktop. First thing this morning, out of nowhere, I started getting an "unable to write the email to the mailbox..." message when sending, thus I could send but not save. And then I realized I wasn't receiving either, on all three accounts in my Thunderbird. I stopped everything and focused on trying to fix this. It's been an all-day, losing effort. So far.

I tried the various quick checks and fixes recommended here and there: I'm running the program as an administrator. I restarted the program. I rebooted the computer. I think I have enough disk space, but to be sure I deleted some bloat from possibly overly large files. I compacted, even though the program is configured to do that regularly. I temporarily disabled my antivirus program. I went into my webmail and deleted all messages that have arrived since my Thunderbird stopped receiving, in case one of them was corrupted. And probably some other attempts as well. Nothing has helped.

And now a second, even worse issue has fallen from the sky. Thunderbird opens. The folder list is where it always has been. The number of unopened messages in each folder is there in boldface, as always, but...the folders are all blank and I get the dreaded popup: "unable to open the summary file...." Have I lost my years' worth of carefully curated emails?

I've tried folder repair. I've deleted parent.lock. Etc. Nothing. Nothing. Nothing.

I will be super-grateful for any wisdom sent my way.

I'm back with an old problem.

When filtering email, it gets interrupted with the error message of:

"The folder "xxxx" could not be found, so filters associated with this folder will be disabled. Verify that the folder exists, and that filters point to a valid destination folder."

Yes, the folder exists.

The previous solution was to change the mail server to imap.googlemail.com. I did that, but connectivity to it has become erratic (it services Germany, Poland, and Russia).

Is there anything else I can do besides use the imap.gmail.com server and keep reenabling the mail filters?

My 'sent mail' has suddenly all disappeared - although still on the mail file server. Inbox mail is fine - but if I send a test message to myself, I get the reply, but the sent message is not saveb. I have uninstalled and reinstalled Thunderbird twice, n - the second time deleting the Mozilla folder under C:\users and then rebooting This happened whilst I was using Thunderbird. I have used Thunderbird for years without problems I have run a virus scan with Malwarebytes, but no problmes showed up. All folders are still vixible on my iPhone

I am about to try reinstalling again. I don't want to have to change email clients.

Any help much appreciated.. Thank you Joan Kemp

Hi, I am using Fibrus email (network name is xxx and network key is yyy). Fibrus uses eero as a modem. I cannot work out the correct server settings in Thunderbird as there doesn't seem to be a place for 'network key'.

Most grateful for any help you can give me.

Simon

(Personal info removed by moderator)

COMCAST Outage 2025 12 17

After finally getting my TB installation up and organized (v140.6.0esr), COMCAST/XFINITY just acknowledged that they are having issues with 3rd party email programs. At least with Mozilla Thunderbird. Sheesh!

My ISP, Plusnet, has recently migrated stored email to a new organisation called Greenby. From the day that Greenby confirmed that the migration was complete, no new email has appeared in Thunderbird.

They said that there was nothing to do, although I had to confirm some credentials such as username and password.

Clearly, there was something to do! How can I restart the download of email from my new Greenby webmail account to Thunderbird?

Sending of the message failed. The message could not be sent because connecting to Outgoing server (SMTP) smtp-mail.outlook.com failed. The server may be unavailable or is refusing SMTP connections. Please verify that your Outgoing server (SMTP) settings are correct and try again.

Seem to get this (or similar) error frequently. It's like the things I set randomly revert or change. Have sent images of settings. I certainly don't know what to do.

I am using Version 146.0, released December 9, 2025, on a Win 11 Pro, v. 25H2 pc. No problems until today. Messages won't download from two AT&T (ameritech.net) accounts. T-bird is not asking for mail key. No change after restarting T-bird; same result after rebooting pc. How do I restore email access? Thanks.

I use Thunderbird as my email client for my remote machine setup through Parallels Client desktop software for PC. After the recent update, every time I want to send an email, the compose window opens along with another browser window that displays my email account page home screen. Before only the email compose window used to open and after sending the email it would close. Now with the browser window that opens every time, i can't send another email until i close the browser. The attachment that i am including in my email also opens in the same browser window in a new tap and i have to manually close them.

How can i go back to just the email compose window to open and not the browser for every email?

Thanks, Yashar

Hi,

Longtime Thunderbird user. Was online last night, emailing (sending and receiving) perfectly fine. Got online this morning - no changes to my computer or Thunderbird, and suddenly am getting this message:

'Thunderbird could not connect to server inbound.att.net. The connection was refused."

I am able to read mail fine from AT&T Mail via webmail or the Yahoo Mail app. This is strictly an issue with Thunderbird and AT&T.

Any other AT&T users having an issue? Any helpful suggestions? If it matters, I have a bellsouth.net email address.

Thanks!

You seem to have addressed this topic well but not simple enough for complete non-techies like me who can really only do "Click X, then right hand click Y, then click Z" etc. Is there a noddy solution I could try? Thanks. Derek

After getting fed up with the Outlook app on windows. I decided to switch to TB. Now i can recieve my mails but can't send. I don't Use VPN and also checked if Windows Firewall is screwing things up. But those are allowed

Without the following. Unable to login to server (SMTP) smtp.office365.com with username *****@hotmail.com has failed (Translated from dutch)

These are my Settings incoming IMAP server: outlook.office365.com, 993, SSL/TLS, OAuth2 authentication, User Name = *****@hotmail.com outgoing SMTP server: smtp.office365.com, 587, STARTTLS, OAuth2 authentication, User Name = *****@hotmail.com

Optus (Australia) emails can't be sent or received by Thunderbird on my PC via my Optus wifi internet connection. I can use emails on my phone via mobile data with wifi turned off (different email client on the phone, though). Optus checked all the settings on my PC with me and they are all correct. They insist that it is a Thunderbird issue (doubtful, IMHO) and that I contact you. Is there an issue with Thunderbird connecting with Optus email? If so. is there any resolution to the issue? If not, can you confirm no problem from your end so I can get back to them (again!)