Thunderbird Community Forum

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 josettethirion@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

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,

Something horrible and time-consuming has changed within this past week to Thunderbird. My version is 140.7 1esr 64bit. Over the past 4 days or so, I've found I cannot scroll down and see the full emails--until I have to use this new pop-up system.

This is definitely not an improvement in my estimation. Is there any way to undo this?

My Thunderbird crash whenever I tried to "save as" an email, save the attachment of an email, attach a file to an outgoing email.

Every time I did the mentioned, Thunderbird prompts the normal window of my laptop's folders, but it disappear in a second with the Thunderbird crash and quit.

This situation happened after I installed MS365 on my laptop.

I did try the below: 1. Reset attachment directory - mail.compose.attach.dir 2. Run in trouble shooting mode 3. Repair folder index 4. Clear cache

Anyone can help please?

Does TBird support plus addressing?

Scenario: I want to reply to email sent "To: markfilipak+joe@...". To do that successfully, in the "Write" dialog, I have to click on "From", scroll down to "Customize From Address...", click it, and add "+joe". (There is a menu alternative: "Options","Customize From Address...".)

If I forget to do that, then my reply does not have "+joe"; it goes out "From: markfilipak@...".

The Issue: When Joe replies to _that_ message, it does not have "+joe", so Joe's reply is trashed. (It's trashed because a filter I wrote automatically deletes messages that do not have "To: markfilipak+<something>@..." in the header.

The sensible way to handle plus addressing is for TBird to recognize plus addressing and to automatically make my "From" header from Joe's "To" header. That way, "+joe" will always be there.

Is there a way to do that?

Thanks Folks! -- Mark.

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

Please Please Please advise how to modify settings to stop copying emails to "All Mail" folder. There are nearly 14K emails in that folder, and it's killing my capacity, I'm getting warnings, etc. Yes, I'm using Gmail.

Yes, I have unsubcribed from it, starting from my account name → Subscribe → unchecked [Gmail] All Mail. To no avail...

Of course, I do not want to delete mails I have saved in my hundreds of other folders. My mail goes back 25+ years, and I want to keep those archives.

Thank you Thank you Thank you!

I use both Gmail and Thunderbird. I can see both in Thunderbird on my PC. I would like to sync my TB address book with Google contacts. I searched a good while on-line and find information about adding a CardDAV Address book. However the instructions mention steps that simply are not available on Thunderbird on my PC. I have the latest version of TB (140.7.1esr (64-bit)). The first step says to "open the Address book, select File>New> CardDAV address book". That is not a choice. Anything in Mozilla support is several years old.

So is this possible or not?

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.