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. >>> That line has now been restored.

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.

I am unable to send an email from Thunderbird to 2 hotmail accounts that I have been communicating with for several years. The issue has only recently started and I can send emails to them from another email account that I have on gmail and any other emails than these are fine from Thuderbird Below is the return message that I receive - can you help

   ""  This is an automatically generated Delivery Status Notification.      

Delivery to the following recipients failed permanently:

  * andyfmorris@hotmail.com

Reason: A message that you sent to the following recipient could not be delivered due to a permanent error. ** The remote server ?? responded with: ** andyfmorris@hotmail.com ??:?? This message was created automatically by mail delivery software on the server .

Reporting-MTA: dns; avasout-peh-004 [212.159.14.20] Received-From-MTA: dns; [192.168.1.81] [51.7.113.34] Arrival-Date: Tue, 17 Feb 2026 11:05:53 +0000

Final-recipient: rfc822; andyfmorris@hotmail.com Diagnostic-Code: smtp; 550 5.7.1 Unfortunately, messages from [212.159.14.20] weren't sent. Please contact your Internet service provider since part of their network is on our block list (S3140). You can also refer your provider to http://mail.live.com/mail/troubleshooting.aspx#errors. [Name=Protocol Filter Agent][AGT=PFA][MxId=11BCD72C9602F57A] [DU2PEPF00028D0F.eurprd03.prod.outlook.com 2026-02-17T11:05:53.185Z 08DE6B964EE3CE26]

Last-attempt-Date: Tue, 17 Feb 2026 11:05:53 +0000 ""

Sehr geehrte Damen und Herren, seit vielen Jahren benutze ich Thunderbird für meinen Mailverkehr – zur Zeit mit der Version 147.1. Beim Posteingang habe ich den Ordner <TU> mit vielen Unterordnern zum Abspeichern wichtiger Informationen eingerichtet. Seit einigen Tagen ist dieser Ordner „verschwunden“ - lässt sich nicht mehr abrufen. Bei der Benutzung von <OutlookWeb> mittels msx@tu-dresden.de ist dieser Ordner wie gewohnt vorhanden. Nach geöffnetem Profilordner habe ich die Datei <global-messages-db.sqlite> gefunden, Thunderbird geschlossen und diese Datei gelöscht. Nach wie vor fehlt jedoch bei Neuöffnung von Thunderbird beim Posteingang der Ordner <TU> mit den vielen Unterordnern. Es wäre durchaus möglich, dass dieser Ordner <TU> eine Größe von mehr als 2 GB mit seinen vielen Unterordnern besitzt ? Inzwischen habe ich beim Posteingang eigentlich parallel zu <TU> einen neuen Ordner <XXX> angelegt, der auch angezeigt bleibt. Bestimmt lässt sich dies bei Thunderbird mit einigen Klicks wieder aktivieren. Für Ihre Hilfe möchte ich Ihnen im Voraus danken. Mit freundlichen Grüßen H. Köcher

Hello, can someone please fix this e-mail address please & thank you.

Following the instructions provided at this web page: https://developer.mozilla.org/en-US/docs/MDN/Community/Community_Participation_Guidelines I e-mailed a code of conduct violation report to the provided email address, mdn-cpg-report@mozilla.com

Actual results:

I immediately received the following e-mail reply, telling me in effect that my e-mail could not be delivered:

Subject: Delivery Status Notification (Failure) Date: Sun, 15 Feb 2026 21:34:30 -0800 (PST) From: Mail Delivery Subsystem <mailer-daemon@googlemail.com> To: [redacted]

Hello [redacted],

We're writing to let you know that the group you tried to contact (mdn-cpg-report) may not exist, or you may not have permission to post messages to the group. A few more details on why you weren't able to post:

You might have spelled or formatted the group name incorrectly. The owner of the group may have removed this group. You may need to join the group before receiving permission to post. This group may not be open to posting. If you have questions related to this or any other Google Group, visit the Help Center at https://support.google.com/a/mozilla.com/bin/topic.py?topic=25838.

Thanks,

mozilla.com admins

[headers, etc redacted]

Expected results:

I expected instead to receive a reply telling me that my e-mail had been successfully received.

Hi there,

I currently have three email accounts set up in my Thunderbird client. I’d like to disable the automatic marking of messages as read—but only for one specific account (mainly for my colleagues’ convenience, as it’s a shared inbox).

In Settings > General, I see the option to turn off "Automatically mark messages as read", but this would apply to all my accounts, which isn’t what I want. I’ve checked the Account Settings for the relevant account and couldn’t find a per-account option. I also looked for an add-on that might help, but so far, no luck.

Has anyone found a workaround or solution for this? Any advice would be greatly appreciated !

Thanks in advance, Cheers.

I recently lost incoming emails to my inbox. I am in the process of setting up a website and had to change the DNS settings to proceed with the website. Since then I have lost incoming emails to my Firefox email. Which also references the domain name. I'm not technical at all so I'm wondering what I need to try to get back to access. I'm wondering if it's something to do with the outgoing server settings ? Any help much appreciated, thanks.

None of the topics suggested fit. I'm having trouble with getting extensions on toolbars. In the customize toolbars window there's a toolbar at the very top of the page that starts with mail, calendar, addressbook, etc. Just for example, the Google Calendar and Outlook Calendar extensions are in that toolbar, but I can't move them to another toolbar and that toolbar disappears when I close the Customize page (either way) and I haven't been able to find a way to get it displayed in other places. That toolbar is very similar to the toolbar that appears on the left side of the Thunderbird window, but that one doesn't include the extra extension buttons that I mentioned above.

Some people in various places have suggested that customizing Thunderbird toolbars is done the same way as in Firefox. But I haven't been able to find a puzzle piece icon anywhere.

By the way, I used to be able to add more toolbars, which I found to be an attractive concept, although that implementation didn't always work so well.

I just got a new Windows 11 computer. After installing Thunderbird 147.0.2 I noticed there were no columns at the top of the message pane as there had been in the past. I read articles about how to add the columns but could not find the column icon or anything in the header area that allowed me to do what the articles recommended.

I want to add the columns for sorting purposes from time to time but I can't find a way to do it. HELP!!! Please?

Thanks, Clyde

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.

After an email update this morning, I went in to look at an old email and nothing was there. Checked all my other folders and they were all empty. How and/or can I get them back. Some were ones that I did not need to loose.

How do I import *.ICS file in a reasonable amount of time. I have appointments in an ics file of less than 1 K in size, typically 700 - 800 bytes in size and they take HOURS to import and do not connect properly then to allow editing the appointment. This is from Baylor Scott and White, a major hospital system in Texas. If there is a problem with the imported file structure, please point me to the correct file structure. I like Thunderbird, but this part of the calendar is very frustrating. Clarence

Hi all,

I am new to a Mac (1 year now) and am trying to make Thunderbird work for me as I have not been happy with other mail clients. I am struggling through a few things.

I like to navigate by keyboard if possible. In the Calendar tab using a month or multi week view, the "[" and "]" move month by month or week by week in multi-week view. How do I move to the next day or two using the keyboard?

A big thank you to all who reply, and sorry if this question has been answered many times before (I did not find the answer in the keyboard FAQ). --Tim

ho appena inviato un post, replica ad una vostra risposta... purtroppo ho concluso con il button "solved the problem" ... per favore, ho giusto ri-raccontato il guaio, non è per nulla solved... non mollatemi, grazie. Giorgio Chiantore, 10015 Ivrea.

Good afternoon, Since yesterday, I have been having a problem where new messages can no longer be previewed or opened. Emails can be sent, but they do not appear in the sent items folder. Everything works fine on my Samsung smartphone with the Samsung app.

Kind regards and many thanks, Marcel