Thunderbird Community Forum

1. Was able to receive emails sent to my address xxxxxx@xxxxxxx.free-online.co.uk, but unable to SEND my replies. Was getting this notification: 'Send message error. Sending of message failed. An error occurred while sending mail. The mail server responded: Unknown sender. Please verify that your email address is correct in your account settings and try again, OK' (see attached). 2. Checked all settings, all correct as used to be before the problem started. 3. At some stage, I tried changing the password in Settings > Privacy & Security > Passwords > Saved passwords > Saved logins to see if that helped. It didn't. 4. I removed the free-online Server from the Saved logins (Provider: smtp://relay.free-online.net, User: xxxxxxx) with the intention of restoring it with a new password - but found I couldn't restore the free-online server. So I decided the best thing to do was to restore the password as it was before and to ask for help here. I will have to check on the webmail until the problem is resolved.

NB1. Free-online is a sub section of Plusnet. NB2. Last year I received an email from Greenby saying something about maybe taking over from Plusnet and that I would be notified if and when I had to do anything. I have not received any such instructions so left things as they were. Many thanks for your help from a not-very-techy so stressed old lady.

Subject: Persistent SMTP block on specific Outlook account (IMAP functional) ​Problem Description: Systematic failure of outgoing emails via SMTP on Mozilla Thunderbird for the address redacted@outlook.be. Crucial Note: Incoming mail (IMAP) works perfectly with the same credentials, proving that the authentication and the password used are correct. ​Technical Data & Actions Taken: ​SMTP Configuration: Server smtp.office365.com, Port 587, STARTTLS (or port 465 SSL/TLS). ​Authentication: Using a 16-character App Password generated after enabling Two-Step Verification. ​Symptom: Systematic rejection of the SMTP connection (Command Error 12 or timeout). Other Outlook accounts configured on the same Thunderbird client and the same internet connection (Belgium) are working without any issues. ​Tests Performed: Complete purge of Thunderbird's password manager, alias verification, and full restart of network equipment. ​Conclusion: Since the reception service is operational and full access is functional via Webmail/Outlook App, the block is specific to the SMTP protocol for this particular account on the Microsoft server side. ​Request: Please lift any security restrictions or reset security flags for the SMTP service on this specific account. My mail for respons : [edited from public community support forum] @gmail.com

(PII removed by moderator)

My husband and I use the same internet provider activ8 and access it through Thunderbird. I have a new computer. Received a configuration code from Activ8 and I can receive emails but not send them. Get the message PEER USING UNSUPPORTED VERSION OF SECURITY PROTOCOL. THE CONFIGURATION TO MAIL.ACTIV8.NET.AU MUST BE CORRECTED. How do I do that? Activ8 says they can't help.

Reguarly with some month between I can´t send email. After many days, which is impossible to use, it is ok without doing anything.

Haven´t manage to send in many days and now it is huge problem.

When I click on send buttom on the email come text about the fail which is 100% wrong.

It say: An error occurred while sending mail. The mail server responded: (then come my email adress): Sender adress rejected: not owned by (the part of my adress in front of @) Please check the message recipient (my email adress) and try again.

This text is 100% wrong because all things is as always! Never changed it. And seeing it in setting it like it should be!

I am almost given up, this come always with months between and that is hopeless.

Please help!

My computer suddenly started the above error message for multiple programs. The local computer shop was able to sort out what appeared to be the root cause and that recovered some things but I still needed to reinstall a number of programs.

The program I am terrified of reinstalling is Thunderbird. All my emails on five email accounts since 2011 are stored in TB and I naturally do not want to lose any of them.

The major problems are the computer is running Win7 Enterprise and I am 82 years old so I am prone to needing things spelt out in greater detail than many others.

Can anyone provide a way to reset the program permissions (preferable) or identify the best way to reinstall and still access all my historic emails?

Thank you

I am using Thunderbird 115.18.0 and Windows 7 professional (no snarky comments please).

All has been working fine for years, but in the last few days, strange thing have been happening:

In the pane with all of my email accounts, the ">" icon to the left of the first account has been disappearing. This meant I could not look at any folders, including Inbox, Drafts, Sent etc and handmade folders. Cured by closing and opening Thunderbird.

I now have two Archive folders, one called Archive, the other Archives. Both empty, neither can be deleted.

Periodically, when the ">" is present, selecting it (to "V"), the list of folders SLOWLY appears, one folder at a time.

Periodically, the bottom of the Thunderbird window, shows a 'downloading' message, of hundreds of files. Several GB of data has been downloaded over a couple of days.

Opening the Inbox folder, the pane with subject, correspondents, date etc has changed the sort order.

Sometimes, all of the emails in this pane have had their font underlined.

Nothing on my system has intentionally changed,

Any ideas what has gone wrong, and how to put things right would be appreciated.

Thanks,

I had two Thunderbird apps on my computer. When I realized that one of them was for organizations, which I don't belong to, I deleted it. But both of the apps were deleted. I then reinstalled Thunderbird, but when I went to send an email, my entire address book was blank. How do I retrieve it and reinstall it ? Thank you.

I have been using Mozilla Thunderbird for decades and they have even contributed a small amount of money to Thunderbird periodically. Just within the last two or three days all of a sudden I have been unable to send emails with my phone. I receive emails, but I do not send them. So I opened up a laptop where I did not have Thunderbird and set it up properly through Spectrum using the incoming and outgoing servers as mail.twc.com. and yes, just like on my phone. I continue to receive new emails, but even with the laptop I was unable to send an email. I received the message"send message error sending a message failed. The message could not be sent because the connection to outgoing server smtp mail.twc.com was lost in the middle of the transaction. Try again."I contacted Spectrum twice and both times they had me try to send a message through their Web server spectrum.net and that message did go through. Of course then their response is that this has to be a problem with the third-party app meaning Mozilla Thunderbird, and they can’t help with that at all. I sure would appreciate some help because I hate to walk away from Thunderbird as well as change my email address after all of these decades.

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?

Hello all:

Transferring Thunderbird from the system above to the system noted above. Follow the instructions from here on the Mozilla Support page (copied both "Thunderbird" directories into the Roaming and Local destination directories. When the destination machine installation opens, it is functional (i.e. it picks up all the existing e-mail accounts, downloads new mail, etc...). The problem starts when we get to the local folders.

All of these have a date and time appended to them in the destination installation. For example, if the original folder is "Prosperity Bank" the destination folder is labeled "Prosperity Bank (2025_09_21 23_06_33 UTC)" and will not let not populate (shows no messages inside).

As I am typing this, it seems I may have identified the problem (or at least part of it). It seems the destination system install is slowly working its way through the local folders randomly (not in alphabetically order), as it seems to be slowly populating them with the old mail stored therein on the original system. It is going very slowly. Very slowly.

Has anyone else experienced this? Is it normal? Is there any way to quickly eliminate the dates now appended to the local file names? (Visually this is very annoying and I do not want to try modifying the individual folder names yet until I'm sure its populated as much as it will populate.)

Thank you for any assistance.

Larry Reese

Windows 10 became unavailable, but I have a copy of the drive it was on. I had tried to install Linux Mint as dual boot and couldn't get to Windows any more. Installed Linux Mint 22 on that drive, wiping out everything that was on it. Now I really want to get all of my locally saved items from the copy of the old drive onto TB in LM22. The profile folders are there, I just don't know what to do with them. FYI, all of my other data files were on other hard drives, so only the OS and apps were on the boot drive.

I am running Thunderbird 147.0.1 (64-bit) on Windows 11 Pro 25H2. I have Thunderbird set up with two email accounts -- gmail and outlook.com (an old msn.com address). Approximately every 10-14 days the msn.com account encounters an error with the message "Command Error 12." When this happens, Thunderbird immediately drops all the local email folders for the msn.com account, and attempts to redownload all email and folders associated with the account. The msn.com account in question is configured for IMAP:

server name: outlook.office365.com Port:993 Connection Security: SSL/TLS Authentication Method: OAuth2

The expected behavior here would be for Thunderbird to display a connectivity error message but retain all local email on my laptop. However, this specific connectivity issue is dropping all locally stored email. I also noticed that the mail columns get reset to default. It appears this issue is causing Thunderbird to delete not just the email but some of the account configs as well.

At present, I do not have a screenshot showing the command error 12 message. I will try to take a screenshot the next time the issue occurs. What is not clear is whether this is an account setup issue or a bug in Thunderbird. Any advice would be appreciated. Thanks.

I can't login to one of my email addresses. It says login to server with username failed. I tried all of the suggestions (using a pop server for example) and none of them seem to work. Please help.

Folder name: BOGUS AI PRAISE-MKTING-BOOK CLUB BULLSHIT I had been adding emailed marketing messages that I knew were fake into this folder for about two weeks. This morning, after a Windows 11 Update, when I tried to add another such message to that folder, the entire file folder was missing. I tried everything I could think of, including looking for help online, to no avail. This folder contained around 500 emails, over 200 of which I hadn't even opened.

I'm trying to find the proper way to revert back to the default location for local mail message storage in TB (ver 140.7.1 esr).

Years ago I set my local message storage to a storage drive on my Win10 PC. I now want to move all of TB to a new Win11 PC but realize I have thing in 2 places - messages on my storage drive and everything else of TB in the default C: drive location.

If I simply change the Message Storage Local Directory back to the default path - will it move my current/old messages to the default location or do I have to manually move things (first or after?)?

I have many years and about 13Gb of email messages that I want to ensure I keep.

TIA