Thunderbird Community Forum

Hi. I'm using Thunderbird for my POP account and it has stopped sending messages. It just says, Sending of the message failed. Peer's certificate has expired. The configuration related to (my server name) must be corrected. What am I to do?

Today - 26/01/2026 - Thunderbird keeps crashing for no reason. I receive a dialogue box to either quit or start Thunderbird again and to add to a crash report. I have been doing this all morning - no response. I have gone onto Mozilla Google search to see if there is a problem - nothing. I have shut down and re-started the computer - nothing happens. Please can you respond and maybe give me a customer service 'live' person who can talk me through this. I have used Thunderbird for over 15 years, but this is defeating me. I am in my late 70's and cannot cope with the way your Community site works. Thank you for your help. Hope to hear from you soonest.

Hello there, I have troubles signing into my email account on Thunderbird. I have a new laptop, therefore installed the program again, as I used it on my old laptop too. When I wanna sign up my email though, it gives me an error message that reads "Anmeldung auf dem Server fehlgeschlagen. Eventuell sind Konfiguration, Benutzername oder Passwort nicht korrekt". I'm writing in English here, since the Support site won't allow me to use the German site for whatever reason. Finding this contact form was also hard. Anyways, the German text translates roughly into "sign in didn't work, probably configuration, user name or password are incorrect". My password is correct, my e-mail is correct, I double and triple checked. It wants a full name from me. My mail account is from t-online and doesn't have a user name. So I entered my full name. Didn't work. I entered my t-online user ID, didn't work. I used only my first name. Didn't work. I tried out both IMAP and POP3 configurations, both lead to the same error message. According to my t-online account, IMAP is supported. One more thing: Before selecting IMAP or POP3, I received the message that my data was in fact found in the Mozilla ISP data base. Please help. Thanks!

Is there a faster way to allow images in incoming messages? Manually copying email addresses to Tools/Settings/Exceptions is a chore when processing a lot of mail every day. If there's maybe an extension/add-on that would be great, though I can't find one.

Many thanks

Hello,

I run Thunderbird 146.01 under Windows 11 Version 10.0.22631 Build 22631... TB pulls messages from a POP Server.

Though I have tried many fixes TB keeps reverting to requiring that I manually run both Spam Sorting, and Filter Sorting, usually after running these functions automatically for about a week.

Might someone suggest a fix that will have some lasting benefit?

Many thanks,

Lothar

Continuation of my prior post: https://support.mozilla.org/en-US/questions/1516342

Thunderbird has a routine problem with being unable to log into various mail servers. I have four accounts and they all seem to share this problem.

Most recent update: I've tested this in Windows Safe Mode, and the problem has not appeared. Since I can't do any useful work in Safe Mode, it's hard to give it a thorough test, but so far so good. Also, I have removed AVG antivirus because it was redundant. I have seen no improvement since it was removed.

Can this problem be resolved?

I have 2 parallel accounts with the same ISP. As of 2 days ago, whenever I try to send mail, I get this message: “Sending of the message failed. An error occurred while sending mail. The mail server responded: Command rejected. Please verify that your email address is correct in your account settings and try again.” I receive mail as normal. Using the other address with exactly the same settings allows me to send normally as I have for the past ten years! Nothing appears different anywhere in the settings. There were no upgrades that I am aware of. I have since found that I can send from my basic little "travel" computer without issue. Any ideas? BTW, using POP mail settings.

I recently upgraded Thunderbird from v140.7-ESR to v147-Release and would be grateful if someone could answer some questions.

After upgrading I noticed there are 3 profile folders even though I am the only user of my Win11 laptop.

Profile Folders 92yfgi88.default-esr - 3.654 GB - 2026/01/23 12:50:27 >> My profile jf63jfuk.default-default - 1.533 GB - 2024/06/05 21:27:32 y9efj7q9.default - 47 Byte - 2026/01/23 12:30:15

The folder y9efj7q9.default only contains 2 files - parent.lock (0kb) and times.json (1kb).

1. Can I safely delete profiles I don't use?

2. Why is -ESR still shown at end of my profile folder name? - I thought it would be renamed when I changed to the release channel version.

3. Can I manually rename my profile folder? - I know I can rename a profile using Profile Manager but this doesn't rename the folder.

4. If not possible to rename my "92yfgi88.default-esr" folder, I assume I can just copy it's contents to another new profile folder and tell TBird to start using that?

5. Can I use Windows File Explorer to delete/rename profiles, or must this be done from within Thunderbird?

Also, any idea why Thunderbird Notifications still show as coming from Mozilla Thunderbird ESR, even though I now use the Release version? I've checked Windows 11 System > Notifications and it is still shown there as Mozilla Thunderbird ESR.. Why? and how to fix?

Thanks in advance..

TB 128 stopped downloading messages from 1blu.de on one 1blu account, another is working.

Switching to pop did not help, neither resetting password on server. Going back to imap did not help. Update to 140.7.1 did not help. In 140, TB connects, searching folders, discovers inbox, but no download of new messages. Inbox is abonniert (subscribed?) and messages are set to loaded to TB.

inbox.msf is updated today, the inbox has a date of Jan 26, latest downloaded email as of Jan. 21, inbox is 3GB and writeable.

In itself, the account at 1blu is ok: the release version (146.0.1) can connect and download messages dated until tonight (=right now).

1blu recommended to delete/reinstall the account but that would mean loosing tags and maybe xnotes.

Any help is appreciated. I write legacy and webextention addons for TB and can run test code in the console or in a temporary addon, if needed/helpful.

Thanks, Klaus/opto

I am trying to create filters for all the spam I have been receiving. It mentioned a tools menu for adding additional filters, but I am not seeing a tools menu anywhere,

How can I retrieve emails I deleted by selecting wrong parameters in the wrong area. I was in Thunderbird > Acct Settings > Synchronization & Storage and saw "Disk Space" settings. Without thinking I selected --> O ... Delete messages more than [ xxx ] [ ^v ] days old and I changed the number to... [ 90 ] days old. Like an idiot, I for some reason thought I was dealing with messages in "Trash"... go figure. So of course I then noticed in my email Accounts... all messages older than 90 days were removed from all of my folders I had set-up. Many of the folders are now blank, empty of emails that I had moved into the separate folders set-up for different information. I've explored tons of solution responses in "Support" but haven't found a solution to my problem. I really need my older emails back... please help! , Ron.

Hello, My SMTP server uses Let's Encrypt certificate. The website with the same domain has no certificate. Thunderbird refuses to connect to my SMTP server. Test connection to the server (STARTTLS) in account settings sais "The secure connection to the server failed" (or similar. I see bg localization). Another server with Let's Encrypt certificate. Test pases. Clicking View certificate shows webserver cert (from DigiCert Inc).

I can't send emails! :)

Regards! Valentin