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When replying to an email or sending a new mail I get the message :- An error occurred while sending mail. Server responded : You need to authenticate when sending mail from (ip address) Please check "message Recipient" and try again. How do I authenticate ? Thanks140.7.1

As the title says, over the last two days Thunderbird won't do SMTP authentication to Outlook. It has worked happily for years and nothing at my end has changed.

I've the latest version of Thunderbird - 140.15.0esr (64-bit) - and this is Windows 11. It works happily from the Outlook desktop so the password is correct.

The authentication method is OAth2 and connection security is STARTTLS. Server is smtp.office365.com and port 587.

Anyone else having issues? Presumably MS have changed something (again)

Has anyone any suggestions on how to resolve?

After swapping to The Bat some years ago I decided to come back to Thunderbird again. So I installed Thunderbird 155.0.1 (64-bit) on my Windows 11 PC, and gradually re-created and connected the the accounts I had on the back. I also installed the ImportExportTools NG addon, then exported my emails from The Bat to Thunderbird. So far so good. However for some reason I created an account twice. There are both for the same GMX account, but one is POP and the other is iMAP. This mistake probably happened after a long session of setting things up and I just forgot about the first account.

I looked through the Thunderbird help and the answer most given was to the Thunderbird menu, select Account Settings, swap to the account you want to delete, and then press the large red DELETE BUTTON on the top level of its settings (next to the DEFAULT button). I've tried this and it doesn't work. There's no confirmation dialog (which is what I was expecting) and if I close and reboot Thunderbird the account is still there.

How can this be fixed?

A few times I have missed messages that have have been inadvertently placed in the Accounts Spam Folder. Is it possible to to indicate that the Spam Folder has contents in the same way contents are indicated in other Account Folders?

Hello, I use the 32-bit portable 153;2 version of Thunderbird. But now when I label a message according to my list of labels by color, the selected message returns to its original color. Labeling no longer works, even though old messages retain their colors well. Thank you for your response. Ph. Costes

I understand that in the immediate future that Virginmedia.com will no longer provide email services for their subscribers is this true.

I can no longer use outlook due to being a basic BT email account user. Thunderbird recognised my account. But now says can find server. It may be my password is wrong in outlook, but it is so long ago, I have no idea of my original password. I’m using the BT Mail app on my iPad and iPhone which works fine, but want my past and present emails on my laptop as well. I’m using windows 10. Any help??

I have downloaded and installed Thunderbird Email on my computer.

I put in my name as requested. Enter my Gmail account and go through all the steps signing in only to get a message that there is an error and I cannot be signed in.

Extremely frustrating to not be able to use this app.

Will be uinstalling immediately.

Hey guys,

So I am trying to create a rule that will delete emails on the server that are 360 days or older.

I know you can go into settings...

>> leave messages on server >>>>>>For at most ,,,,,,,

But from what I have read that only deletes emails on server from when they were downloaded into thunderbird.

I am new to thunderbird so that wont work for me.

So I went into message filter....thinking this would work

>>>>>age in days > is greater than > 360 days >>>>>>>>>>>Delete From Pop Server

But nothing happens???? Help!

Your input is appreciated

After a long explanation, I tried to add a file and lost everything. Starting over! After using TB for over 30 years, I accumulated a large number of personal folders to archive files to. Due to confusion on my part about pass words in Proton Mail and their Bridge, I had to reinstall my ProtonMail account into Thunderbird. Because all my personal folders were connected with the old "account" name, I didn't remove it, and the new addition seemed to be working fine.

After doing some house cleaning to remove duplicate and obsolete files, I wanted to move the folders attached to the old account name, under the new name. I thought I could carefully move my personal folders from the old account, back under the new Protonmail account. Sadly, that doesn't work like that. What I did find was that the original folders which come under the original "account", were created with an older version of TB, which put them in a folder on my HD. But the new default folders ("inbox", "draft", "sent" etc.) are mirrors of the Protonmail Bridge, which is NOT what I want.

So I need someone that knows how to either place the old folders back under the NEW "account", or how to create new folders that ARE on the HD, and then move the files from one place to the other.

Just to help clarify, here's the location of the old folders as per the "properties" info.

mailbox:///E:/thunderbird data/thunderbird/yetudx3p.default/Mail/Local Folders/Friends & family

You can see the address for this folder is on my Drive E: I can go directly to that address on my drive E and see each of the files.

imap://gshantz%40protonmail.com@127.0.0.1/Folders/2009

This folder is from the NEW account of Protonmail - bridge, and is obviously the web address of Protonmail. It is NOT editable, unlike the above location on my HD E:.

Any help or suggestion would be greatly appreciated, gshantz

Aloha. I'm helping a friend with setting up a new Windows 11 PC, and cannot get Thunderbird to connect to Spectrum's servers. I spent an hour on the phone with Spectrum support and they just gave up and said it must be an issue with Thunderbird. Here are the details:

- Brand new Dell 24 All-in-One EC24250 - Windows 11 25H2 plus all additional fixes. - All Dell drivers updated. - Thunderbird V155.0 64-bit

If I click on 'Get Messages' after a while I get: "Connection to server mail.twc.com timed out". I've gone into the config editor and changed mailnews.tcptimeout from 100 to 500 and still get the error.

In the Account Settings | Server Settings | Test server connection I get: An error occurred connecting to mail.twc.com:993.

I've tried this with both setting up a brand new account in Thunderbird, and also via copying the 'Thunderbird' folder from %appdata%\roaming from her old machine.

Email configuration (from Spectrum).

IMAP Settings Server name: mail.twc.com Port: 993 user name: abcd@hawaii.rr.com Connection Security: SSL/TLS Authentication method: Normal password

SMTP settings Server Name: mail.twc.com Port 587 Connection Security: STARTTLS Authentication method: Normal password

Can anyone help me troubleshoot this scenario?

Mahalo, Harry Z

Just started Thunderbird and all my accounts and mails are gone. All empty. I tried to import from default: C:\Users\Korisnik\AppData\Roaming\Thunderbird\Profiles\fjv3tdcd.default and now I have mails until 2025, all from year 2026 is gone. What to do???? please answer to [redacted email from community support forum]

In TB 155.01 when I click on Delete the email leaves my Inbox but does not display in the Deleted folder. If I look at Properties in the Deleted folder it shows the correct number of messages in there but the messages themselves do not show in the right hand window. Thus there is no way of seeing what the messages are, just the total quantity in the folder.

This morning, my email Inbox is empty. I use Thunderbird for four email accounts, and three of them are fine, but the fourth one has an empty Inbox this morning. I didn't (intentionally, anyway) move the emails anywhere, and they do appear to be in the All Mail folder, so I didn't lose them entirely. But I keep my emails mostly in my Inbox and they aren't there anymore.

Any ideas what happened to make them disappear and how I can get them back to the Inbox?

Thanks!

Здравствуйте! 1. Почтовый клиент стал показывать в папке "Входящие" по 10-15-20 копий одного и того же сообщения. 2. Когда-то была создана папка "Pending"во входящих сообщениях. Сейчас почтовый клиент сам по себе поместил ее в папку "Удаленные", причем во входящих двух разных почтовых ящиков. Создать эту папку как отдельную во входящих не удается. 3. Удаленную папку "Охрана труда" почтовая программа также поместила как отдельную папку в удаленных и воссоздает ее снова при запуске почтового клиента.

now i am getting mail but my dad and my brother both said they are sending mail and it says undeliverable I tried sending to my self and it came through I have Thunderbird through Comcast. i see mail in Comcast that is coming through so i do not know why. the only thing i could think of was they tried yesterday when the update was going through i received a mail at 7.15 this evening so i have no idea why it would bounce back did nothing to change anything

Having established a new Outlook account I cannot sign into it properly with Thunderbird - I get authentication failures each time despite all settings apparently being correct, IMAP enabled in the web browser view of the outlook account and so on. Oauth2 set and all server settings good. I have been over and over things. Tried various suggestions of the web to no avail.

I have tried unsuccessfully with three separate machines - two Microsoft 11 laptops and an iMac. All fail.

I can access the account and send/receive emails from a web browser and I have got it working okay with an iPhone, an Android tablet and a Microsoft email client - but not with Thunderbird. I even get a browser popup on the iMac when I open Thunderbird asking if I am trying to sign in - I say yes and it says I am all signed in - but the email doesn't authenticate. I have passcodes all set up etc.

A separate Hotmail account does work with the same Thunderbird client and has the same server settings (apart from the username obviously).

I am at a loss how to resolve this other than move to a different email application.

Any ideas?

I have three email accounts. One is with a btinternet.com domain, and Thunderbird 153.2.0 has started not fetching emails from it while getting all the others. I've removed and reinstalled the account and things work fine for a few days but then it stops again.

All the security settings, etc., seem correct, and I'm not getting any error messages, just nothing happens.

Any thoughts from out there?

I have Thunderbird 153.2.0esr which runs 2 Email filter (on Inbox and on Outbox)

These filters worked for years.

Suddenly, about at the end of July 2026, the stopped working.

I suspect that one of the latest release of Thunderbird make them stop working.

Is it possible? Any suggest?

Also the filter log registry is empty.

Environment:

• macOS, Apple Silicon (aarch64)
• Thunderbird: 155.0.1 (aarch64), Release channel
• Email hosting provider: Hostinger
• SMTP server: smtp.hostinger.com
• SMTP configuration: Port 465, SSL/TLS, Normal Password authentication

Problem: Incoming email via IMAP works normally, but Thunderbird cannot send any outgoing email.

The error is either:

“The connection to Outgoing server (SMTP) smtp.hostinger.com timed out.”

or:

“Sending of the message failed. The message could not be sent because connecting to Outgoing server (SMTP) smtp.hostinger.com failed. The server may be unavailable or is refusing SMTP connections.”

Troubleshooting already performed:

• Webmail can send emails normally.
• Thunderbird can receive emails normally.
• SMTP settings and username have been verified.
• Port 465 with SSL/TLS does not work in Thunderbird.
• Port 587 with STARTTLS was also tested and does not work.
• Tested with a different network/mobile hotspot — same issue.
• Tested Thunderbird Troubleshoot Mode — same issue.
• Updated Thunderbird from 155.0 to 155.0.1 — issue persists.
• Direct TCP connectivity from the same Mac was tested successfully:

nc -vz smtp.hostinger.com 465 → succeeded

nc -vz smtp.hostinger.com 587 → succeeded

Therefore, the SMTP server is reachable from the Mac on both ports, and the same mailbox can send normally through Hostinger Webmail, but Thunderbird fails to establish/use the SMTP connection.

Since sending was working normally before the Thunderbird update and stopped afterwards without any SMTP configuration changes, this appears potentially related to the recent Thunderbird update.

Could you please advise whether there are any known SMTP/TLS/socket issues with Thunderbird 155.x on macOS, or any additional diagnostics/settings I should check?