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As of Oct 12 2026 I also have this issue. About a week before the 12th I was getting messages that I needed to sign into my RCN account which I would do and it just kept asking me. A few times each night to start then right before it shut me out I had over 50 of these messages just flooding my screen. I never did get a screen shot of that message, but did for the 2 error messages I got later once it shut me out.

I shut down my computer the night of the 11th then when I signed back in on the 12th I could not send or recieve any emails. SOmething similar had happened before, but when I shut down again it went away. This time it did not. I then tried to access my emails thru the webmail I can access, but that also had shut me out. I also tried my tablet, a borrowed smart phone, but I could not access anything for my emails. I troubleshooted with my email company and my internet company, but they found nothing.

Then I shut off the wi-fi on the smart phone and bin go I could access the webmail. But I still cannot find anything on what to do to fix this.

I use RCN for my email, Spectrum for my internet. It is a POP3. Running Thunderbird version 153.5 Oesr (32 bit) Meadow, which says it is up to date. I have norton 360 anti virus & do not use VPN. I disabled my Auto-protect and firewall on the Norton and that did not change anything.

I have sent the error messages to RCN and also troubleshot with Microsoft and had some hints, but nothing has come of that yet. Here are the screen shots of the only 2 things I ould capture. The error message was when I was trying to access my email thru Thunderbird. And it came up every time I tried to send messages, not that does not show up anymore and nothing happens when I try and send anything. The second one was when I was trying to access the RCN webmail and it would not let me in on anything I used. Until I shout off the WI-Fi. Then the smart phone could access my webmail account.

Current Thunderbird setup: Computer: Pop3 Phone IMAP

Until last week, I could leave the emails on my phone all day until I accessed them on the POP3 setup on my computer. That would remove the emails on the server and when I went back to my phone, it would show an empty inbox. Now, the emails do not clear out of my inbox on the phone, and I have to delete them manually. This happens on both the production version and the Beta version. Also, accessing via webmail, the inbox will be empty after accessing email on my computer.

Thunderbird has been receiving emails on my PC from Bell Sympatico for years, then suddenly stopped in July 2026 without my changing any settings, and I have to go to the Bell server instead.

I used compuserve.com for email since more than 20 years ago when the internet is accessed by dialling in. However, compuserve.com is absorbed into AOL quite a number of years ago, and since then I have difficulty in reading my email via Mozilla Thunderbird. I need to login my compuserve.com account via the AOL website, and the mail files cannot be download to my computer for storage. I noticed in the web at the time that compuserve.com account users are complaining about the difficultly of getting the email via other email readers as well Is Mozilla Thunderbird has an update that can read the emails account in AOL or compuserve.com? My computer is using window 10, Version of Mozilla Thunderbird  : 102,0,3

Many thanks

Good Day,

When sending email to a list in my address book, I get the error stating that its not a valid email address and to verify it is in the User@Host format. However, if I right click on the list name and choose EXPAND LIST and it then correctly displays all the email addresses and names, and it sends completely fine and without issue ?

Any ideas have to fix that issue ? Thank you in advance for your assistance.

I believe this is because Plusnet are transferring me to Greenby, and I am now required to sign in using my full email address, i.e. ***@madasafish.com. I can't figure out how to change this, it will only let me change my password. Please can anyone help -urgently!

I have now the version 158.01 (64-bit) with Windows 11. My Gmail account has stopped sending emails. This started a few days ago, while I had the version 158.00. The error message is that connection to the outgoing server smtp.gmail.com times out. With the help of AI, I have created a test profile, and it sends mail, though it is a bit slow in saving them to the Sent folder. With the help of the AI, I have tried maybe 30 things to troubleshoot, but none worked. I have many accounts on Thunderbird, and re-installing all of them would be time consuming. Any suggestion?

The note said "You are receiving this message because according to our records, you have recently logged into your . . . Google account using an outdated protocol (IMAP). This is usually through an external application such as Apple Mail or Outlook. We will be applying some security updates on October 28th, including disabling access to email via IMAP. Apple Mail and Microsoft Outlook use IMAP so these will no longer work after IMAP is disabled. You should start using the web interface on your computer and the GMail App on your iPhone immediately to make sure that you don't miss any emails.

So does this mean I won't be able to use Thunderbird any more?

I have Thunderbird installed on a desktop and laptop (both running Windows 11) and an Android phone. I can no longer receive emails on the two PCs, though the phone still works OK. Webmail works fine on all three devices. I have tried all the remedies I can find on the web, but so far without success. When I send a test email to myself it goes out OK and appears in my webmail, but does not appear in my Sent box. I tried doing Repair Folder on my desktop Inbox. This caused all the existing messages in the inbox to disappear, though the folder size still shows as 400Mb. I have a secondary email address which I use occasionally (a gmail address). This is still working OK. All help gratefully received. Alan

I have received emails from today, 10/21/26 but noted that emails from 10/19 and 1020 are missing, Can you please figure out why for me. I use Thunderbird/ Freedom. Thank you.

I stopped getting e mails 9 days ago on Thunderbird. I found out that plusnet that used to have me had passed on to greenby. I can get onto greenby but i would prefer to be on Thunderbird because of my saved business e mails. Mike

I have Proton Mail, and Proton Bridge. It was working until Yesterday. Starting Yesterday, New emails would show up in the Web app, and the ProtonMail Desktop App, but would not make it to the Thunderbird Inbox. The first email that did this arrived at 1:30PM on 10/19. When a new email arrives, a new email windows notification will popup in the lower right hand corner. I checked Spam, and it is empty (I find this hard to believe). My phone also displays a new mail notification.

I know Thunderbird is receiving the emails. I can find the new emails by using "Quick Search", and searching for the email address of the sender of the new email. The results are completely without formatting, and do not indicate what folder they are in.

For example: I have a Gmail Account (redacted@Gmail.com), and I sent a test message to my ProtonMail address (redacted@Proton.me). That email contained the subject line "Ping 10/20" and it contained my auto signature. If enter "redacted@gmail.com" into the quick search, and I hit the return button, it only finds a message I sent about 7 weeks ago.

If I then click on the magnifying glass icon, a new tab opens up with the results. It displays the first 10 results of 54 results searching for "redacted@gmail.com". At the top of the results is my "Ping 10/20" test email. I could not find the folder name where my "Ping 10/20" test email is located on this results tab.

I see that the text "Ping 10/20" is a hyperlink, so I click it. The tab shows up, and strangely, it show the email and one reply. No reply was received by the Gmail account.

I have done troubleshooting of the ProtonMail bridge. The fact that the email is found somewhere in my thunderbird installation, I don't think ProtonMail Bridge is the issue.

Today when trying to send an email I get Sending of message failed. The mail server responded: Mailbox full. I use an Outlook address. I have emptied my trash, spam, and sent items folders along with moving many of the contents of my folders to the Local folders.

I tried the automated setting up - several times but get the error message below, I tried changing the authentication but same result.

I tried the Help here: https://support.mozilla.org/en-US/kb/thunderbird-and-hotmail - but it didn't help!

I have the settings it shows for Outlook - but it doesn't work! When I "Continue" I get Authentication error. Show less

"Unable to log in at server. Probably wrong configuration, username or password.". It hasn't asked for a password.

I can login in to Outlook webmail and receive messages. Please help. I'm not overly technical but not totally ignorant either! Thanks, Isobel

So long as I investigated, the problem is,

After version154, received emails in Japanese encoded by 8bit causes misconversion (mojibake). Emails encoded by base64 is not misconverted. Only 8bit encoded shows the problem. Version153.5 is no problem. Version154 and newer shows the problem.

Here are OK/NG by sender/receiver combination. Sender version154 8bit - receiver version154 - NG Sender version154 base64 - receiver version154 - OK Sender version154 8bit - receiver version153 - OK Sender version154 base64 - receiver version153 - OK Sender version153 8bit - receiver version154 - OK Sender version153 base64 - receiver version154 - OK

Emails encoded by base64 is OK, but some senders can encode by only 8bit. I cannot find how they can use base64. It would be helpful to know to use base64 encoding in version154 (or later).

However, the best way is that version154 (or later) can read 8bit encoded email in Japanese. I would like to thank anyone who help the problem.

After today's update, my email is not loading from Gmail. Last delivery was 5 a.m. It is now after 5 p.m.I have restarted Thunderbird 3 times, restarted my computer and restarted the modem to no avail.

Hello This is a Thunderbird on Windows 11 question If I select a file, right click and then click on "Send to" >"Mail Recipient", Windows tell me

There is no email program associated to perform the requested action. Please install an email program or, if one is already installed, create an association in the Default Programs control panel.

But Thunderbird is installed, up and running and is set as default for MAILTO (see image)

So what could be the problem?

Luckily, files can be loaded into messages using the "Attach" command in Thunderbird if that gives you a clue

Thanks in advance for any help