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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.

Hi all,

After thoroughly searching this database, I could not locate an answer to the issue I am facing, although there seem to have been several similar cases.

My former university has recently decided to delete alumni email accounts, so I am using Thunderbird for email transferring from university to GMail (added both accounts to Thunderbird and then began copying emails and folders). Transfer is slow, depending on the server capabilities etc., but I am going folder by folder and so far it has been fine. I began the transfers a week ago.

Last night I noticed my Thunderbird inbox for my school is not showing anymore. The profile folder is only showing one file (.msf) for Inbox, instead of what should be, in my understanding, two files.

Thunderbird is still communicating well with the university email server because I made a folder rearrangement on the university webmail service (outlook.com) and it showed on Thunderbird. In addition, all my Inbox emails appear fine on the university webmail service (outlook.com).

Any ideas? This is obviously important and urgent.

Thank you in advance.

When sending an email using the keyboard shortcut, the settings tell me that I can set TB to give me a confirmation prompt. Why can't I get a confirmation prompt when using the Send button? Is there any way to make TB do that?

I set TB to run a spell check before sending, and that gives me an opportunity to cancel the Send operation. But it only works if the email contains a misspelling.

Thank you.

At lunchtime today I started getting emails with no header sender or other info. It is just blank and the emails dont show just a load of source info in the message body.

I keep getting this message "Unable to write the email to the mailbox. Make sure the file system allows you write privileges, and you have enough disk space to copy the mailbox." every time I log in, try to delete an email that has already downloaded, and every time I click get messages to download messages.

No messages have been downloaded since two days ago. I did go on the web version of my email and deleted all emails from that time period in case there was a virus so it's not that. I strangely started when I ignored the compact folder message sever times. I did however try to compact the folder from the file menu, as well as cleared the cash and emptied the trash.

I made sure I had the latest update as well. I am thinking the software is corrupt at this point.

Two nights ago I uninstalled ExpressVPN from my system at the instruction of one of their "support" people. My computer immediately lost the ability to access half of the websites I tried to visit and Thunderbird wouldn't send or receive email. I rebooted and that fixed every issue, but since then, Thunderbird no longer checks for new messages for any of my accounts. If I manually instruct it to check, it downloads the messages with no problem. I don't use any add-ons, and I'm using the latest version on a Windows 11 PC. I have already tried deleting global-messages-db.sqlite, repairing each mail folder from within Thunderbird, clearing the cache, and running an install of the latest version. I have also tried changing the setting for each mail folder to alter the interval for message checks by a minute just to see if that would jog it, but no luck. I've looked at various other help threads for this and am out of ideas. Thanks in advance for any help.

My Spectrum password was changed and now I cannot get direct access to TB. For some reason TB is not linking up with Spectrum password. I get a popup panel saying "Login to server Mail.TWC.Com with username jomar159@hvc.rr.com failed" Retry Enter New password Cancel I have 2 accounts on TB 1 is wmarks1 and the other is jomar159@hvc.rr.com HELP

I quite often get this message, though it tends not to be a problem later "Unable to write the email to the mailbox. Make sure the file system allows you write privileges, and you have enough disk space to copy the mailbox"

One of the solutions seems to be Compact a File. How do I do this?

I have Mozilla Thunderbird email application with Windows 11. Recently I have problems opening some email texts, but not all. I do receive the mails and heading, but the contents are not displayed. This goes for some mails, and I do not see any connection as to which ones open and which ones don't. I would appreciate your advise. Bo Dahlberg

I am trying to set up a filter to copy the last sent email to another folder. When I do this I get a copy in the inbox from where the email has been sent. The copy ends up where I asked but the copy in the inbox is annoying and I can see no reason why it is doing this. Any pointers? Many thanks.

Hi there! I and my colleague encounter some bugs with Thunderbird and we would like to seek your advice in regards of the issue.

1. <user a@citizen-systems.com.hk> was supposed to get a cc copy of the email sent by <user b@citizen-systems.com.hk> at Mon, 12 Jan 2026 09:35:19 +0800 but it never reached. The receivers, namely <user c@systems.citizen.co.jp> and <user d@citizen-systems.com.hk>, however, were able to get the mail. <user d@citizen-systems.com.hk> and <user a@citizen-systems.com.hk> are working at the same office and under the same network. Network provider checked the protocol, router, traffic and firewall are working as normal.

2. <user e@citizen-systems.com.hk> found a number of emails that she kept at "Inbox" disappeared on 12 Jan 2026 morning +0800.

She is unable to find it anywhere at her whole mailbox but has to ask the senders to resend them to her.

It would be very much appreciated if you can check and advise how to prevent the issue from happening again.

(PII redacted by moderator)

Hello. My name is Chris Bottle and I live in Australia. In the last couple of days I've discovered that I'm unable to send emails. I've checked my IMAP settings are they are all correct. My email provider is Telstra Australia. When I send an email I get a reply back "An error occured while sending email. Outgoing server SMTP error. The server responded; Connection refused - OB119 .103.224.52.151 is blacklisted in Abusix Mail Intelligence and then two lines of text prefixed by https;/lookup.abusix and further text. I checked with Telstra and after much checking they could find nothing their end. I'm not that computer literate and freely admit that this problem has bamboozled me. I hope somebody can help with this problem. Many thanks. Cheers, Chris

i am crying here i have changed my password for Comcast several times but i think ih ave screwed up The smtp server i am not sure wast do do there this is what i have can yu please tell me what to do please help i t will not et me send please

Trying to set up new smtp account. Out tech team says we did everything correctly.

I tested by trying to send email to dlibman72@gmail.com. I get "relaying" error.

SMTP Server: smtp.mailgun.org Our servers listen on ports 25, 587, and 465 (SSL/TLS)