Thunderbird コミュニティフォーラム

I have been using Thunderbird for years. My current version is 158.0 (32-bit). In recent months Thunderbird has become increasingly weird and annoying. These problems have occurred individually, not all at once, and each persists--that is, they are all and always present.

1. T'bird's counts of messages in folders is always much higher than the actual counts. 2. I tag messages with color, but T'bird deletes the color tags within a day. 3. Clicking a message doesn't change the message from Unread to Read--that is, the title stays bold. I can change the read/unread indication by clicking the button, but the change doesn't happen automatically. 4. If I drag a message to my wife's T'bird inbox, the act removes the message from my T'bird inbox, but it doesn't always remove it from the inbox at the Server. 5. Deleting a message from my T'bird inbox often also deletes the message just above it. This is the oldest problem, and when it first occurred I found that if I closed and immediately reopened T'bird the message would reappear in my T'bird inbox. Now it does not, although the message might still be in my inbox at the Server. 6. While I am reading a message, the list of messages often pops up to the top (oldest) message. The message I was reading doesn't disappear or otherwise change, but I have to scroll back down to it and click it again in order to delete it or move it to another folder.

These problems are more than annoying. Can anybody help?

I sent email, email goes out from thuderbird but copy is not saved is "sent mails", its only for one receiver, for all other it works, why? before it work for this receiver too

i am migrating from Outlook to Thunderbird and cannot see how i can migrate my tasks: i have trawled the internet but can only find out-of-date info about old versions of TB or using 3rd party tools: how can i sync TB tasks with Outlook or at least import tasks from Outlook for access in TB?

Since 2 day when I attach a document always unknown software aception (0xc0000417)on place Ox00000000501

NVIDIA Systemsteuerung nicht gefunden pops up I dont wont KI on my computer

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.

Updating to the most recent [159.0 (64-bit)] update zapped my email account (gmail) settings. No, I haven't tried troubleshoot yet or re-entering all my IMAP settings. :) (I will when I can shoehorn the time.) My installation (64-bit) on the appropriate Windows version has had no problems for years, & updates have worked consistently (through both ap & OS updates, until this specific update.

My question right now is, has anyone else run into problems with this issue? I know it's not that much to go on, but I'm in a hurry & need to see if anyone else has experienced it.

TIA for any/all info. :)

Bill N.

I use HTML as my signature. It has been working just find, but lately when people reply to me, their messages were coming in blue text. So today I changed the: Settings > General > Plain Text Messages > Quoted text formatting from blue colour to black (I have no idea how that was set to blue in the first place). that is all I did. Image attached of the change I made.

In any case, after that, when I tried to send a new email my HTML signature no longer displays the correct font (Pristina) but shows only variable text. The HTML file is not corrupt, it still looks fine in the actual file I saved, but, Thunderbird is changing it somehow. Even when I look back at sent files, Thunderbird is showing me the variable text and not Pristina.

Any assistance would be much appreciated. With thanks, NM

Hello ! Thunderbird is runing on Mint Linux. There is a Email account on Austria A1 (Telekom) This account has primary a number such as aon.999999999@aon.at and you can make an alias on it just as "your_name@aon.at". Tihs account has been reading with thunderbird for 2 Years. now A1 has posted, they have to change the number. So they did but the alias has stayed the same. Before this I have made 3 local Archives with thunderbird named 2024, 2025 und 2026 in which I transfered the elder Emails I wanted to keep. After the Change from A1 the local Archives still can be seen by their names but when you klick on them you dont see any Email. What can I do to get them back ? I had a look at the dataset where the data are stored, and in Editor I still find the Emails, but not in thunderbird. thank you for your advice - and sorry for my poor english. grretings from Austria

A few days ago, when I opened Thunderbird, it began downloading all folders and emails from my server provider ( bringing the folders to date) I already removed the account and the database twice to see if it was a database issue, but it keeps refreshing all my folders and emails, which is a huge amount and takes a long time to complete. Any idea how to troubleshoot or fix this? Thanks

I am trying to migrate my Thunderbird account from PC Windows 10 to a new PC Windows 11. The installation selects my provider and settings correctly but when I try and sign in, I get the above message. I have not the first idea where to start there. any help would be appreciated. I still have a copy on a windows 11 laptop that I can use to enter settings, but I can't get that far with the installation. Any help would be greatly appreciated.

Hallo,

ich bitte um Hilfe, seit dem letzten Update von Thunderbird auf 159.0 (64-Bit) sind meine Mailaccounts verschwunden. Eins konnte ich wieder einrichten, das von T-Online bringt als Fehler ständig "Fehler bei der Authentifizierung" obwohl alles korrekt ist. Thunderbird kann sich automatisch die Serverdaten für IMAP holen, aber sobald ich das Passwort eingebe kommt der Fehler. Das Passwort habe ich jetzt bereits geändert, dennoch funktioniert es nicht. Was kann ich tun?

When I move messages I want to save to local folders I have created, sometimes they are greyed out, and back in my Inbox

This also happens in the Sent folder

I have had problems accessing my email server (EveryMail). Problem started about 2 weeks ago. Was no problem before. I am using unified folders. Sometimes a folder property (inbox for instance) shows all email accounts but nothing selectable. Other times an account might have only inbox selectable, other times all account labels are visible. Selecting options for deleted folder only shows inbox for most email accounts. Similar for spam.

Hello,

I was composing a message in TB 159.0 when a shower of duplicate messages appeared. Each message in the central pane was present eight or ten times. In my Tools menu I have an option to Remove Duplicates, I think it's an extension I installed years ago but I can't remember clearly. When I ran it a popup appeared telling me no duplicates could be found, which is ridiculous.

I restored my profile from backup and the problem went away.

I would like to know how I can avoid this issue in the future and, if it happens again, how I can eliminate the duplicates,

Alan.

Unable to log in at server. Told: Probably wrong confid, username, Password. Can't proceed, don't know what to do! Perhaps nearly there? Need your help. Thank you.

I rarely do any detail adjustments, if any, to Thunderbird so I am completely at sea on it! I have not been able to identify my Thunderbird version but must be recent.

I think I have managed to get almost there but need your help. I have so much to do but can't proceed with the work that desperately needs doing.

Your help would be much appreciated. I am not a natural PC worker, I have managed to extract myself from MS Windows because I don't need all their diverse complicated bits of software. I just want to get on and do the things that really matter. Linux, Thunderbird have been doing all I need. Using Linux and Thunderbird is a breath of fresh air Malcolm Sanderson.

Since yesterday when I open Thunderbird to check my bigpond emails on my laptop I get a message that says "Enter your password for mail.bigpond.com" - I've never had to enter a password in all the many years I've been using Thunderbird on my lap top. I can get the emails on my phone and on Telstra webmail but I prefer Thunderbird. Also get a message that says "Mozilla Thunderbird login timed out" When I put in the password I use for Telstra webmail it says "Host contacted sending login information" but then I get another message Login to mail.bigpond.com with user name [redacted] @bigpond.net au failed Retry...

Not sure if this is connected to not getting emails on my phone for a week and going in to Telstra yesterday where they fixed that problem...

WIN10のPCで、Thunderbirdを長年使用してきました（ささやかに寄付もしました）。３年前に故障したのでHPのPC（WIN11、M2のSSD内蔵）に変え、Thunderbirdをインストールした時にはそのまま何の支障もなくメールが開通したのですが、今回多分内蔵のM2のSSDの不調でか、WIN11が立ち上がらなくなりました。他のSSDに差し替えたところ、ネットその他のソフトのインストールや動作は回復したものの、Thunderbird による so-net のメールやり取りができなくなりました。 「メッセージ受信」しても「サーバーpop.so-net.ne.jpとの接続で認証に失敗しました」となってしまいます。何回か試し、DLし直したり、「認証方式がOAuth2になっているか」確認したりしても原因がわかりません。メルアドは「kjm@cf7.so-net.ne.jp」です。一つ思い当たるのは、インストールし直した時だったかに、「パスワードを入力」という画面が出てきたことです。前回の時はなかったので、自分のメモにもありません。新たに今はパスワードを入力するようになったかと、それなりのワードを入力したものの、「パスワードが違う」とはねられました。 このメルアドはいくつもの認証先や連絡先であり、このまま使用できなくなるのは大変困ります。どうか解決方法があればお教えください。メールが受信できない相談なので、お返事はこのページに表示されるのでしょうか？ ちなみに、苦し紛れに別のメールソフトをＤＬし受信しようとしましたが、やはり「認証に失敗しました-ERR[AUTH]Authentication failed.」となって受信できませんでした。