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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.

Ok, This is a bit of a question that seems to have many answers but none that have ever worked for me. I have in the past 12 months probably formatted my PC 4 times, and I have at least 12 profiles on Firefox nightly, not to mention the rest of the family. It's not really a problem to redo them every time, but it is just a painstaking simple process. If I could just backup the profile folder, copy it move it change it whatever, it would be nice and simple, even to transfer from one pc to another in the house, but every time I try, It fails. Copy the Userdata folder, copy the entire firefox folder, blah blah blah, never can I do it. I believe it has something to do with security that you can't just copy and the entire profile folder, but some way to backup the profiles exists surely? One that actually works. Cheers All!

I get the message: We're Sorry Firfox had a problem and crashed. We'll try to restore your tabs and windows. To help us diagnose and fix this problem, you can send us a crash report. I sent the crash report multiple times.

I added a screenshot of my MacBook Air info.

The details are: AvailablePhysicalMemory: 1700704256 AvailableSwapMemory: 0 BackgroundTaskMode: 0 BuildID: 20260216153405 CrashTime: 1773448580 DOMFissionEnabled: 0 DOMIPCEnabled: 0 HeadlessMode: 0 InstallTime: 1772203700 LastStartupWasCrash: 1 MacAvailableMemorySysctl: 75 MacMemoryPressure: Normal MacMemoryPressureCriticalTime: Unset MacMemoryPressureNormalTime: 1773448580 MacMemoryPressureSysctl: 1 MacMemoryPressureWarningTime: Unset MozCrashReason: MOZ_CRASH(NS_ERROR_OMNIJAR_OR_DIR_MISSING) ProductID: {ec8030f7-c20a-464f-9b0e-13a3a9e97384} ProductName: Firefox PurgeablePhysicalMemory: 248750080 ReleaseChannel: release SafeMode: 0 SecondsSinceLastCrash: 15923 StartupCacheValid: 0 StartupCrash: 1 StartupTime: 1773448579 SubmittedFrom: Client Throttleable: 1 TotalPhysicalMemory: 8589934592 UptimeTS: 1.104864563 Vendor: Mozilla Version: 148.0 This report also contains technical information about the state of the application when it crashed.

Moderator note: This question has been edited to fill the Firefox version field (based on the info submitted).

If it ain't broke, don't fi(o)x it. Never try to be too clever. I cannot log out of OUTLOOK.COM, then after goodness knows hot long, it says that I have been kicked out and need to login again. CRAP!!!!!!!

I am running Thunderbird 140.8.1esr on macOS Tahoe 26.3

I created an IMAP account in Thunderbird to replace a POP account

I want to copy the Thunderbird message filters from the POP account to the IMAP account

I read articles on Mozilla Support and these said to copy the msgFilterRules.dat file but I cannot find this file

How can I copy the message filters?

I've created a passkey for logging in to Google.

When trying to log in to Google within Firefox on my Pixel 9 phone, I'm automatically taken to the page where I should be prompted to enter my passkey, but no prompt actually appears, so there's no way for me to actually enter my passkey. (See attached screenshot.)

To be clear, I can still tap "Try another way" and log in using other methods, such as via an approval prompt sent to my other devices.

This problem does not happen on my Samsung tablet. When I try to log in to Google within Firefox on my tablet, I'm given the choice to log in via various methods, and if I choose to use a passkey, I *am* given a prompt to enter my passkey.

Any idea what the problem could be?

I get this error ALL THE TIME from TB. Sending of the message failed. The message could not be sent because connecting to Outgoing server (SMTP) smtp-mail.outlook.com failed. The server may be unavailable or is refusing SMTP connections. Please verify that your Outgoing server (SMTP) settings are correct and try again. Copilot says that TB is NOT recognizing my personal Outlook email account as a viable SMTP account. Been on line with Copilot for couple of hours without success. Does anyone at Mozilla have anything to offer me?

Lost my Passwords on my desktop and can't recover them through profile manager, I found them on my android phone and want to recover my passwords from there, but am worried if I try and sync to the desktop, the desktop might overwrite the passwords in the phone.

Hi Had some problems with the computer. According to Microsoft the dll error was caused by the new Adobe acrobat. Trying to fix this problem some of the websites in Firefox are having now problems. EXP. Kohl's Error code: SEC_ERROR_REVOKED_CERTIFICATE. Home Depot Oops!! Something went wrong. Please refresh page. This is only happening in Firefox with Windows 7, Firefox version 115.33.Oesr 64 bit. When I access these two websites on Chrome in the same computer everything is fine.

What is causing these errors in Firefox????? Can you please help!!!!!

Amy

On my Linux machine, I exported the public key for an email address in Thunderbird 140.8.0esr (64-bit) into a file. I transferred the file to my Windows 11 machine via Warpinator.

On the Windows machine I am running Thunderbird 148.0.1 (64-bit). In Account settings>End-to-End encryption, I click Add Key>Import an existing OpenPGP key>Select File to import, and then I select the file.

I get an error message: Error! Failed to import file.

I'm surprised. I would think that going from one installation of Thunderbird to another would work this way. I am concerned that I won't be able to read incoming encrypted emails without the key working.

Can someone help me?

Thunderbird--All of my current year INBOX emails disappeared. I have tried repairing the folder, deleting INBOX.msf and restarting including in troubleshooting mode, reinstalled Thunderbird. None of these actions changed the situation. Is it possible to retrieve these messages?

The INBOX folder is much larger than the INBOX.msf folder, so I'm thinking the message info is in there?

I;m using Windows 10.

Good morning . . . I have recently switched from an old Windows 10 machine to a new macmini, and have switched my Office 365 account over to it. Simply stated, Outlook is not working, and I have no desire to continue with it. Will Thunderbird suit my needs? Will it allow me to import my old contacts and emails, both from my Windows machine and the new MacOutlook?

Since changing to a new internet service provider, I can no longer print form Firefox. My internet router uses the same username as password as my previous router.

There is a folder in my Downloads folder ('~/Downloads') called 'thunderbird.tmp' Whenever I delete it it reappears whenever I open Thunderbird. How do I relocate this because I like to keep my Downloads folder neat? I have not found an option for this anywhere in settings on the app.