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Thunderbird version number: 148.0.1 Mail provider: Yahoo Client OS: Windows 10

The issue and steps I tried to resolve: On 1 Jan 2026 I switched from Outlook client on my Windows 10 PC to Thunderbird 146.0.1. I did not import any user data from Outlook but started with a clean install of TB for the new year. I use yahoo.com with POP3 as my email provider. Server Settings: Server Name "pop.mail.yahoo.com", port 995, SSL/TLS, OAuth2 Outgoing Server: Server Name "smtp.mail.yahoo.com", port 465, SSL/TLS, OAuth2

it all worked fine and I was very happy with the setup. Then from early to mid-February I was unable to use my computer. When I finally accessed Thunderbird again, it connected to Yahoo and showed that approximately 800 email messages would be downloaded and started downloading them. After downloading about 100 messages, Thunderbird timed out and I haven't been able to get it to work since.

I have read and followed or tried to follow these articles plus others that I may have forgotten about (not listed in any particular order) - OAuth2 Authentication for Yahoo, AOL and ATT | Thunderbird Help - including all the steps in Please check the following before asking for support - POP access settings and instructions for Yahoo Mail | Yahoo Help - Automatic Account Configuration | Thunderbird Help - Manual Account Configuration | Thunderbird Help - Thunderbird and Yahoo | Thunderbird Help - Send and receive messages in Thunderbird | Thunderbird Help - Can no longer get emails | Thunderbird Support Forum | Mozilla Support - Emails suddenly stopped downloading to Thunderbird 140.2.1esr | Thunderbird Support Forum - Get Messages | Thunderbird Support Forum | Mozilla Support - Cannot receive messages | Thunderbird Help - Problem with Thunderbird working with Yahoo Mail acccounts. | Thunderbird Support Forum

I have removed all messages from the Yahoo inbox and tried to find one or more messages that may be affecting the download. I don't know the best way to determine that.

I use Windows Defender for my antivirus. I don't see anything in Defender that blocks or scans email messages which would prevent downloads, although I could be wrong about that. if this might be the issue, please provide some guidance about how to check Defender.

I have uninstalled and re-installed Thunderbird. In the process I downloaded the setup file for Thunderbird Setup 148.0 and installed that version. It later auto-updated to 148.0.1. Before installation, I removed all external connections from my Yahoo account and completely removed Thunderbird from my PC, including the profile and profile.ini. When I reinstall and switch the account to POP3, Thunderbird captures the App password from Yahoo and connects just fine. But it still times out while attempting the first download of a message. The first several times it timed out, an error message was displayed but now it doesn't show anything. Except no messages are downloaded.

At this point, I don't know what else to try. Since I don't have much experience with Thunderbird, I don't know how to troubleshoot the process (logs to look at, etc.). I don't want to go back to Outlook but I need the email client to work and download messages. Any help would be much appreciated.

I need a filter on a message to FULLY FINISH before a next message starts to be filtered. The "help" (quotes because it's an abyssal crap) says that simply ending the filter with Stop Filter Execution does it - but that's simply NOT TRUE: calling a console program in the filter, I can see five DOS boxes opening at the same time with five messages matching, i.e. the filters on the next message DID NOT wait! So... what can I do??

All of the above is because I'm getting "Too many simultaneous connections on the server". I'd like to limit the concurrency, but it only seems to be possible in IMAP, while this connection is a POP. Why only IMAP??!

We tried installing Thunderbird on two PCs, both running Windows 11, but with unsatisfactory results. In July 2025, we bought a 15-inch HP PC running Windows 11. Thunderbird was installed, and the sending and receiving functions worked correctly with one domain name and three email addresses linked to that domain name. In January 2026, we bought a Lenovo T14 PC running Windows 11. We tried installing Thunderbird with the same domain name and three different email addresses linked to that domain name. Result: On the T14, it was impossible to install the third email address; only two addresses could receive and send messages correctly. Furthermore, the 15-inch HP PC now receives messages but can no longer send them; the connection is rejected by the server. Analysis: Apparently, there is an inability to coordinate the two PCs for Thunderbird. Question: Windows 11 had numerous updates between July 2025 and January 2026. Do both PCs need to have Thunderbird installed the same version of Windows 11 ?

i was trying to change my password to correspond with my other server so i thought changing my password was just to do that but i removed even the primary one that was made 15 years ago and do not have it written down . so now i cannot open up my thunderbird emails or send anything because i do not know the primary password and you guys do not show anywhere i can change that without knowing my primary. which is a joke.

Home Internet speed via cable 500 Mbps. When checking the Internet speed through the Firefox browser (version 133.0.3), incoming and outgoing about 250 Mbps. That is, the browser cuts the speed twice. When checking the speed through Google Chrome (version 145.0.7632.160), the Internet speed is about the declared 500 Mbps. Please help solve the problem with Internet speed through the Firefox browser.

Using Thunderbird, when updated to version 148 (64 bit) the highlighted color is dark and does not contrast to the text color (black) so it is hard to read. How to change the color? or the color of the text?

I'd like to reduce the size of my profile file xxxxxx.default . it is currently 17.2 GB. If I delete several of the folders in the "Local Folder" (example "sent mail 2010"), will the file size shrink or does it only expand to fit the folders.

Hello, I get oftem spam mails with a header like the following: from:Singles50 subject:Momenti speciali insieme per gli over 50 Reply-To:reply_to@miracel001.entrydns.org>

I tried to create a filter adding as personalized condition "Reply-to" that Thunderbird saves in the msgFilterRules.dat as: condition="OR (\"reply-to\",contains,@miracel001.entrydns.org)"

There is no way to get any filter working, do you have a suggestion on how to fix this issue ?

Thanks

I reinstalled Windows and downloaded the browser again. I logged into my account, turned on synchronization, but none of the data was synced. I am absolutely sure that synchronization was enabled on my old browser. I tried turning it off and on again, but nothing helps. Please help me get my data back!

Firefox does a good job of filling in username and password prompts. Occasionally, it doesn't. The sign-in prompt for American Airlines is an example. Go to AA.COM and click on the "Log in" button. The prompt box labeled, "AAdvantage® # or username", is not filled in; but the prompt box labeled, "Password" is recognized and filled in. There must be something about the wording or the HTML used for the first box that obscures the requested information.

Duck duck search via Firefox has become painfully slow, although if Google search is used the speed is OK. I have cleared caches, cookies etc without any improvement. Firefox 148.0.2, Windows10. Is this a recognised current problem?

I've tried setting up Thunderbird archiving according to the documentation to save archived messages locally, and in the same hierarchy they had when I archived them. That is, if I have:

INBOX

   Box1
   Box2

... etc. then archiving would create a parallel structure in Local Folders

However, this isn't working.

I select "Keep message archives in Other (Archives on Local Folders).

For "Archive Options" I select "A single folder", "Keep existing folder structure of archived messages" and "Recreate inbox folder".

However, when I archive something, Thunderbird just creates a folder "2026" (this year) and puts the message in there.

Why are my settings NOT working?

- Tim

I have been unable to access any secure sites since I installed Norton 360 Antivirus. Whenever I try to access a secure site I receive the reply: Secure Connection Failed Error: PR_END_OF_FILE_ERROR I have tried all of the repairs listed on the internet but none have corrected the fault. I have also tried disabling Norton but also without success I have also tried uninstalling and re-installing Firefox but without success Can you suggest any other methods to correct this fault

with this new version i lost everything i need to get back to an older version and get all my extentions my bookmarks back all my s desktop items that i had linked to firefox are gone i can no longer get face book or anything back to firefox book marks every thing i had with firefox

and