Thunderbird Community Forum

Hi,

For both servers imap.exmail.qq.com / imap.263.net, when I click on the email subject in the email list during downloading processes (many emails headers are being downloaded but email body downloading is not completed), the email is broken without any content (only header).

I go to the web email server and move the email to another folder and then move it back to inbox. Then I delete the same email in Thunderbird and donwload again the email again, it's completely downloaded with the email body.

I don't have any issue with eM client or Outlook for such issues. Any possible setting to solve this issue?

Thanks.

Issue is with spectrum server mail.twc.com. Error message sending and rec e mail. "Outgoing server (SMTP) mail.twc.com failed. The server may be unavailable or is refusing SMTP connections." "Server timed out" Server settings are correct. need help!!

Windows 10 Thunderbird Version 159.0 (64-bit)

Today, Nov. 5, opened Thunderbird & got the Error message: Unable to write the email to the Mailbox. I have no idea why this happened. Turned off the antivirus for email, but that did no good.

Thunderbird worked fine yesterday

My two Optimum email accounts (POP3) stopped sending messages. See attached error message. They are still working on a different computer with the exact same settings and Thunderbird version (Windows 10 on both too). I also have Outlook and Gmail accounts all still sending fine. Sending from troubleshooting mode and clearing the startup cache didn't help. Any clues what I can try?

Hello, I am experiencing repeated freezes in Thunderbird 153 ESR on Windows 10. I have been investigating this problem since mid-October 2026, but have not been able to identify the cause. Thunderbird is essential for my daily work, so I would appreciate advice on identifying the cause and restoring stable operation.

1. System environment - PC: dynabook R63/B - OS: Windows 10, 64-bit - Thunderbird: 153.6.0esr, 64-bit - Mail provider: @nifty (Japan) - Incoming mail: POP3 over SSL/TLS, port 995 - Security software: Super Security (Japanese security software) - Mail storage: Local mbox files

2. When the problem started Thunderbird worked reasonably well until September 2026. The freezing problem began around mid-October 2026. Windows Reliability Monitor recorded Thunderbird as "Stopped responding" on October 19, 2026, at 9:48 a.m. This is the earliest recorded incident I have found, although the problem may have started earlier. Thunderbird update history: - September 18: 153.3.1esr - October 1: 153.4.0esr - October 14: 153.5.0esr - October 21: 153.5.1esr - October 28: 153.6.0esr The first recorded freeze occurred after the update to 153.5.0esr. However, I have not established that the update caused the problem.

3. Symptoms Thunderbird becomes unresponsive and usually has to be forcibly terminated. During these freezes, Windows Task Manager often shows Thunderbird using approximately 30–40% CPU, repeatedly around 39–40%. Freezes also occur when Thunderbird is using only about 1.1 GB of memory. On other occasions, memory usage has increased to approximately 2.56 GB. The problem occurs under several different conditions: 1. During manual POP3 mail retrieval. 2. After repeated manual mail retrieval operations. 3. Approximately 30 minutes after a single mail retrieval, even when Thunderbird is left idle. 4. Sometimes after replying to messages or copying messages to other folders. 5. In both normal mode and Troubleshoot Mode. 6. Sometimes during the first mail retrieval after starting Thunderbird. Other Windows applications generally remain responsive when Thunderbird freezes. Restarting Windows sometimes restores normal Thunderbird operation temporarily, but the problem returns.

4. Troubleshooting already performed I have already tried the following: - Reinstalled Thunderbird from the official website. - Created a new Thunderbird test profile. - Disabled extensions. - Disabled hardware acceleration. - Disabled global search and indexing. - Removed all active Thunderbird message filters for testing. - Disabled the anti-spam component of Super Security. - Disabled automatic mail checking and automatic downloading. - Tested manual mail retrieval in Troubleshoot Mode. - Reduced the size of the Inbox from approximately 4.1 GB to 2.4 GB. - Performed a full antivirus scan, which detected no threats. The new profile initially worked, including several successful POP3 retrievals, but the freezing problem later returned. Reinstalling Thunderbird did not resolve the issue. The anti-spam component remains disabled for testing, but the problem continues.

5. Windows error records Windows Reliability Monitor recorded Thunderbird as unresponsive on October 19, 2026, at 9:48 a.m. Windows Event Viewer also recorded an Application Hang, Event ID 1002, on October 30, 2026, at approximately 4:23 a.m. The affected executable was thunderbird.exe, version 153.6.0.0. These records confirm the application hang but do not identify its underlying cause.

6. POP3 communication Earlier POP3 logging confirmed that Thunderbird connected to the @nifty POP3 server and received a CAPA response. However, I have not identified which POP3 or internal Thunderbird operation was active at the exact moment of the freeze. I have not collected a process memory dump.

7. Potentially related Mozilla bug reports I found two reports that may be relevant: - Bug 2080699: POP mail retrieval becomes unresponsive in Thunderbird 153.4.0esr. - Bug 2031744: Freezing potentially related to mail index (.msf) files and background processing. Some symptoms are similar, but I cannot determine whether they have the same underlying cause.

8. Questions I would appreciate advice on the following: 1. Are there known POP3-related freezes or high-CPU problems in Thunderbird 153 ESR, particularly after the October 2026 updates? 2. Could background mail processing, folder maintenance, or mail index files explain a freeze that occurs while Thunderbird is idle? 3. Could interaction with antivirus software or Windows networking components cause these symptoms? 4. Are there diagnostic steps that can help identify the cause without repeatedly freezing Thunderbird or risking existing mail data? 5. Would this information be more appropriate as an additional comment on an existing Bugzilla report or as a separate bug report? I have already spent considerable time testing different configurations. I would prefer to avoid repeating tests that have not helped. I have a backup of my Thunderbird profile and would like to preserve my existing mail data.

Thank you for your assistance.

When trying to launch Thunderbird it gets stuck on "connecting to imap.comcast.net". App Version 102.0.1 GRE Version 102.0. Windows 10 on home laptop. I tried launching in safe mode and got the same thing

I had to upgrade my phone and in the process the passwords were lost. Starting over. Now I cannot adjust thunderbird to get anything. It is supposed to go to an area allowing password update but all I get is a blank screen. Any help is appreciated.

I was referred here from Thunderbird Bugzilla report 2081665.

We are experiencing a recurring problem with Thunderbird 153 on several Windows workstations in a business environment.

The important point is that the problem also occurs with completely new Thunderbird profiles created from scratch. It is not limited to migrated or old profiles.

On one workstation this has already happened to three separate Thunderbird profiles.

Typical sequence:

1. Thunderbird 153 is installed. 2. A completely new profile is created. 3. Mail accounts are configured manually. 4. Everything initially works normally. 5. After some time the profile begins to malfunction. 6. Thunderbird Settings no longer open/respond. 7. The address books still exist, but address autocomplete when composing a new message stops working. 8. Creating another new profile temporarily fixes the problem, but the same behavior can return later.

Troubleshooting already performed:

- Troubleshoot Mode - extensions disabled - tested without the existing prefs.js - rebuilt Thunderbird caches and profile UI state - recreated indexes/databases - completely removed Thunderbird from Program Files, AppData\Roaming and AppData\Local - clean Thunderbird installation - clean profile created from scratch - Thunderbird executable and profile paths added to Kaspersky Endpoint Security trusted applications/exclusions

Removing prefs.js from an already affected profile did not restore the Settings window.

A clean test profile initially works correctly.

We have also encountered this behavior on other workstations. Some users have more than 100 message filters and many folders, so rebuilding profiles repeatedly causes significant administrative work.

Several affected computers had Windows user accounts renamed in the past.

We also experienced a separate issue where the Attach File dialog stopped appearing while drag-and-drop still worked. Bugzilla identified this as the already known Bug 2077590, so I consider that a separate issue.

For comparison, after completely cleaning Thunderbird from an affected workstation and installing Thunderbird 115.3.1 with a clean profile, the same workstation currently works normally.

Because freshly created Thunderbird 153 profiles can later develop the same problem again, simply recreating the profile does not appear to be a permanent solution.

Environment:

- Windows workstations - Thunderbird 153 ESR - Kaspersky Endpoint Security - multiple IMAP accounts - business environment

What diagnostic information should I collect from the next affected profile before replacing it?

I can provide:

- Thunderbird Troubleshooting Information - Error Console output - profile file names/sizes/timestamps - Windows Event Viewer logs - sanitized prefs.js - comparison with a working fresh profile

Bugzilla report: 2081665 Known separate attachment bug: 2077590

WIN 10 independant SSD. (yes i refuse to run 11)

HOW is it posssible in 2026 imprting the contacts/addresses from a prior application is still such a mess?

I have copied, pasted, imported etc and NO CONTACTS. WHY? how does this not work, I have used ai, tutorials etc and still a mess.

I use the native import under tools, Point to my old appdata profile and still nothing.

While i am here,, how in 2026 can the colors still blow? honestly,, why is my email body still 255 white and only the nav colume an inbox changes? Or is it me?

Thanks, Simple Jack

I'm trying to upload less than a gigabyte of images to my send storage but am getting the following error: "you don't have the key to decrypt this container"

This is my own storage space.. I've already generated my own key. Why would it be saying this? I see there is also supposedly an option to upload/share files via send natively in thunderbird via a dropdown menu from the "attach" menu, as show here in the list of features. However, this option doesn't appear in my thundermail. Yes, I've installed the Thunderbird pro addon.

What is happening...

I can not down load Emails from Yahoo to Thunderbird. Every things was fine as of Aug 26th. On Aug 27th with no changes to any system settings the Yahoo Emails would not down Load. I am running Win 10 on my system. I disabled the antivirus. Reloaded Thunderbird - no effect.

I have since deleted Thunderbird and then reinstalled latest version of Thunderbird (154.0) . I re-entered my password. I checked the OAuth2 settings and they are set as described in the support article "OAuth2 Authentication for Yahoo, AOL and ATT".

Message bar at bottom of Thunderbird screen shows: Myaccountname@yahoo.com:Downloading message 1 of 7 The emails do not down load - then after a few minutes - a no messages to download message flashes and then blank - nothing

I am out of Ideas. Anyone?

In einem meiner Postfächer sind alle Unterordner verschwunden unter TB. Auf dem Handy kann ich alles sehen, in anderen Postfächern auf dem PC stimmt alles.

Ich habe alle verfügbaren Tips probiert seit ca. 4h.

Im Verzeichnis von heute scheinen alle Daten vorhanden zu sein, siehe Bild. Die Dateien und Ordner von gestern sind aber grösser, siehe 2. Bild. Im Postfach auf TB sind sie aber gar nicht zu sehen.

Was tun?

Gruss, Dirk

My emails download ok from the server at Greenby. When I try to send a reply from Thunderbird, I get an error message: Login to server mail.madasafish.com with username anniedunn@madasafish.com failed.

I have tried entering my password, retry, nothing works - in the end I click cancel and get this message.

Sending of the message failed.

Unable to authenticate to Outgoing server (SMTP) . Please check the password and verify the 'Authentication method' in 'Account Settings | Outgoing server (SMTP)'.

Please can anyone help, it's very frustrating.

(I can send replies from the server)

Every entry in my address book is duplicated. I don't know how this happened. All are in my Personal Address Book. No entries in any other address books.

What can I do?

habe E-Mailkonten bei 2 verschiedenen Providern seit es Thunderbird gibt. Seit dem letzten Update holt Thunderbird nur noch Mails von einem (immer dem gleichen) Provider ab. Stoppe ich das Programm und starte es wieder wird die Post von beiden abgeholt. Aber nur das eine mal nach dem Neustart.

I am using the correct password but it keeps saying " Login to server imap.comcast.net with username [redacted]@comcast.net failed.". I hope someone can help. Thanks.

In spite of my settings (see image attached), since about a week ago, T'bird has not reliably shown the unread message alert nor shown the unread symbol on the task bar.

I am still running Windows 10, but as of yesterday every time I open Thunderbird it resets my settings and spends hours re-downloading every email that I have. It constantly tells me that the connection to the server has failed and that all my passwords are wrong. Nothing is wrong with the server and none of my passwords are incorrect. After about 2 hrs, it completely re-downloads every email (I have multiple accounts) and I can continue to work like nothing was ever wrong in the first place. However, if I close out the program, it starts all over again. It randomly picks an email account and requires that I start from scratch and reset them up. Other times they are there like nothing happened. I have restarted my computer multiple times, it continues to do this.

Thunderbird will display older email, but will not retrieve new email. It puts up a message "downloading message 1 of 140". That second number continues to grow. It was 76, then 138, now 140. I cannot retrieve new email. That email address is [redacted] @att.net.

I suggest you reply to me at [redacted] @gmail.com.

Fred Bohle