Thunderbird Community Forum

I have used Thunderbird with the same email account for years, creating subfolders and moving emails to the subfolders with no issues.

With Thunderbird 153.0.1, after creating a new subfolder in the account, when attempting to move emails to the new folder, I receive the following error:

"Thunderbird: The current command did not succeed. The email server responded: APPEND invalid flag list"

My Thunderbird, from Debian is:

140.13.0esr

I've often wondered what the point of 'extended support release' (I think) really means. It sounds retrograde. Should I switch/upgrade?

Thunderbird not connecting to server. It says timds out and an error occurred connecting to mobile.charter.net. I can neither send or receive emails. This started 8/20/2026

I have a new PC. I have added five email accounts, three different hosts, with some difficulty. Thunderbird finds the details for others but then refuses with the message Authentication error. Unable to log in at server. Probably wrong configuration, username or password.

I added Thunderbird by copying from my old PC. The hosts for those not yet added are the same as those added.

This is the message I get when it does not go. I contacted Spectrum and they told me to check Thunderbird.

Sending of the message failed. An error occurred while sending mail: Outgoing server (SMTP) error. The server responded: p-impout004.msg.pkvw.co.charter.net cmsmtp 73.238.167.193 blocked. Please see https://www.spectrum.net/support/internet/understanding-email-error-codes for more information. AUP#Out-1130.

I recently migrated to Linux and was able to reinstall my Thunderbird account. However in the previous MS windows version I was able 'choose 'the font as well as other basics for each account signature. In the version I now have it is purely a default font. I tried the forum solution which was to create a message in html then copy it in- didn't work. i don't want to have to add a file everytime when it wasn't necessary before? I want a different signature for 5 different purpose accounts. Why can't I do this in this version of Thunderbird? I also no longer see what font I am in. I just created a dummy email and chose a font. I doubt that will be in place for my next message ie it doesn't offer a default option as outlook would

I have been using Thunderbird on my PC for years and when I got my last PC, I found a article to help me move my files. I am now looking for instructions on how to move my Thunderbird files from the PC to the Mac so I can continue using it as I have been.

“My Spectrum email address is [redacted]@charter.net. Spectrum webmail can send and Thunderbird can't receive or send. The outgoing server is mobile.charter.net and the connection times out. I tested the connection from my computer and ports 587 and 465 both respond successfully. Thunderbird is set to No Proxy. when i tried to send today, it gave me this message, "Sending of the message failed. The message could not be sent because the connection to Outgoing server (SMTP) mobile.charter.net timed out. Try again." i contacted spectrum about this and now when i try to send, it says nothing and the message never arrives.

Hi,

I'm running the latest version of Thunderbird 140.12.1esr on 15.7.7 (24G720) on an M1 processor.

I'm witnessing Memory leak > Thunderbird who usually use 800MB jumps to Gb up to 60Gb

It makes this version unusable.

Here is a loom of the incident: https://www.loom.com/share/0b8e661b42d64d749d80adfd71fd1e04

+ a screenshot

Anyone can help ?

Best Olivier

Latest version of Windows 11 Thunderbird has stopped displaying the message body in the message pane ( right side of the screen) . I have another email client that displays the message body perfectly. It does display the message body of any messages save in a folder but will not display newly received messages in the pane. When I click on the message sometimes I get a white blank screen in the message body display pane. HELP!

In Thunderbird, I have several email folder names that were changed, and I also created new folders, but I cannot see them after restarting Thunderbird. How do I get these folders back? In the past, I have gone to the server of my email provider and fixed this sort of issue there. This time I have not been as successful. How do I get my missing email folders back?

I have been using Thunderbird successfully for sometime and since yesterday there were no new emails in my inbox. This coincided with Thunderbird being upgraded, so I am told. So, I tested by sending an email to myself but TB kept assuming my old email address was valid (died last year) and any attempt to get in and edit my address failed because it kept thinking the old email was was still valid. So, I installed Betterbird, hoping it might work but it copied over my profile, etc and it had the same problem! I guess I could look far another email client but I want to stay with Thunderbird.

Any suggestions please. Robin

I have successfully added five ntlworld.com email accounts in Thunderbird but my two personal ones keep coming up with Authentication error. Each time the screen shows the details of the account found automatically so the information is coming from somewhere.

Advice I gratefully received was to Disable the account hub in Settings / General, then add the account from New Account, and use an application specific password assigned via your email provider.

Virginmedia no longer seems to acknowledge ntlworld accounts but says they are talktalk. However, talktalk says they do not hold the accounts.

I do not understand how I can disable the account hub in Settings when it has not loaded.

I cannot understand why two of the accounts do not load.

Thank you for the advice on copying the Thunderbird folder, which I have done. However, what is failing is the adding of further existing email accounts. I enter the Account name, the email address and the password but I still get Authentication error. I have, after some difficulty, succeeded in adding five accounts with three different hosts. The further accounts I wish to add use two of the hosts of the successful additions.

I have just used a saved email address to write an email. When I went to send it the send failed because the from account was an old account I do not use anymore.

How do I change saved email addresses so they do not use the old account.

Why would this happen.

I checked which account I was using at the time and then repeated the process with the same result. I was using my current account.

Recently I moved from a Thinkpad X1Yoga running Mint and Windows 10 to a Thinkpad P14s running Kubuntu and Windows 11 Pro 25H2. On the Win11 side (which behaves differently from Win10), there are installation issues affecting both Firefox and Thunderbird.

Win 11 Settings lists: under Apps > Installed apps

• . . . (other apps)
• Mozilla Firefox (x64 en-US) 154.0
• Mozilla Maintenance Service 153.0
• Mozilla Thunderbird (x64 en-US) 153.0.2
• . . . (other apps)

under Apps > Default apps

• . . . (other apps)
• Firefox
• Firefox
• . . . (other apps)

That is, Default apps lists Firefox twice (though not as "Mozilla Firefox"), but Thunderbird not at all. This causes two problems:

1. It's not clear which Firefox to choose for browser protocols.
2. There is no Thunderbird to choose for mail-related protocols,

Can someone tell me why the Installed apps and Default apps list differ, and how to set the appropriate defaults for Firefox and Thunderbird?

Thanks, John