If you use the operating system facilities to copy the profile, every character is copied. That includes filters. If transferring a profile to a new computer, these steps work:

https://support.mozilla.org/en-US/kb/moving-thunderbird-data-to-a-new-computer

here is the info in brief steps:

1. ensure thunderbird is NOT running on old machine
2. enter %appdata% in search window on task bar and press Enter key
3. this should open windows file explorer in Appdata\roaming folder
4. highlight the Thunderbird folder and copy to external media
5. ensure thunderbird is installed on second computer and NOT running
6. enter %appdata% in search window on task bar and press Enter key
7. you should be in Appdata\roaming folder , copy&paste the exported Thunderbird folder there. This may prompt to overwrite an existing folder of same name. allow it
8. start thunderbird and all should be there

Well, I did everything that you mentioned and I still don't have the filters in the target computer. I did see another post that mentioned the msgFilterRules.dat file, so I checked my target computer. For some reason I have duplicated data in my imapmail folder in the target. The original file has the proper filter data in it, the duplicate doesn't. I'm going to try uninstalling and reinstalling Thunderbird and see if that solves the problem.

Well, that proved fruitless. I deleted the app, restarted, reinstalled and still wind up in the same place, with duplicated data in the imapmail foilder. I'm going to give it one more go of uninstalling, then I'm going to purge the Thunderbird folder from %appdata%/Roaming if it exists and reinstalling. If it fails again I'll find a better email client.

Failed again. I don't have the patience to try and make this work when it should be seamless. I'll find another email client.

re :I deleted the app, restarted, reinstalled and still wind up in the same place, with duplicated data in the imapmail foilder.

I have no idea why you did that as there are very few issues that get resolved by uninstalling a program, expecially since the issue is in your profile folder and has nothing to do with the program.

If you performed the steps as advised then you should see identical info on both, but as you do not then clearly you did not follow the steps correctly. Most people make the mistake of not exiting thundrebird before any copy or pasting is done - no Thunderbird should be running on either computer. Others paste the Thunderbird fodler into the wrong place or do not delete the original from the computer where it's being transfered into. So first we need to establish the correct profile location on computer one (has ok filters) and on computer two (the one needing filters).

You have two computers - What OS are you talking about ? Are they both Windows OS ?

When you installed Thunderbird on second computer - did you get a download from the official webpage?

• https://www.thunderbird.net/en-US/thunderbird/all/

Or Assuming you are using Wndows OS....did you get an install from the 'Windows App Store' because that option is a bit of a pain as it puts the profile in an unexpected location.? This info is important.

Let me clarify what I've done to try and resolve this problem. My original installation is on a Windows 10 computer and I'm trying to get Thunderbird set up on Windows 11 on another machine, hopefully mirroring what's on my Windows 10 installation.

I did follow the steps to get to the Profiles folder and went up 3 levels to /Roaming, shutdown Thunderbird, verified that it was not running in Task Manager and copied the Thunderbird folder at that level on the Windows 10 machine.

Having completed that step I loaded Thunderbird onto the new Windows 11 computer. I suspended the installation when it asked me to create an account , shut down Thunderbird and verified it was not running in Task Manager on the Win 11 machine. When I navigated to C:/Windows/Users/Lou/AppData/Roaming I found a thunderbird folder, which is not the same as Thunderbird. You cannot overlay that folder with a lower case "t" with the one captured on my USB drive that has a capital "T'. I tried renaming the lower case folder with the proper uppercase letter and when I copied the data into it I found duplications of imapmail and default folders in the Profiles folder. The filters were present in one of the imapmail fiolders, but Thunderbird wasn't recognizing that entry. I also tried uninstalling and reinstallingThunderbird from the Windows 11 machine and just copying into /Roamimng/Thunderbird with the same result.

So, I havce a history of over 40 years experience in the computer support field, in which I've guided numerous clients through arcane procedures. I bvelieve I've followed everything to the letter, and it still doesn't work. Perhaps you need to simplify the procedure to simply copying a file from place to place, as I did with the address book......Unfortunately I'm stuck with Thunderbird because I have some filters which require OR functions that are not provided by other freeware products.

On Windows 11 computer: Where did you get the Thunderbird download ? This information is important. Did you get it from here: https://www.thunderbird.net/en-US/thunderbird/all/ Or did you get it from the 'Windows app Store' ?

When you were choosing what to download, did you select for 'Windows OS' ? Did you select 'Thunderbird Release' OR 'Thunderbird Extended Support Release' ? What version does it say you are using in 'Help' > 'About Thunderbird' ?

I Googled Thunderbird download, which gave me this result - https://www.thunderbird.net/en-US/download/. I don't use Windows App Store as a general rule. In Windows 11 I'm using the Thunderbird Release channel, whereas in Windows 10 I know I'm using Extended Release because of an addon for Bitdefender that I can't seem to get installed in Windows 11, yet anyway.

re :When I navigated to C:/Windows/Users/Lou/AppData/Roaming

That sounds incorrect.

C:/'Windows' folder should not contain 'Users'

That 'Windows' folder should only contain data used by the OS.

'Users' is in 'C' not Windows' - so something is not correct.

Do you have this: C:/Users/Lou/AppData/Roaming

You're correct. The actual path is C:/Users/Lou/AppData/Roaming. For some reason Windows 11 elected to name my C: drive Windows so I mistakenly added that as a level in the path.

I had to rebuild my computer for another reason and having completed that process I managed to FINALLY get this done. For anyone else who might have the same trouble, here are the steps I followed.

1. Open Thunderbird on the source computer. 2. In Thunderbird click on the hamburger menu in the title bar and select Help, then Troubleshooting Information. 3. Scroll to Profile and select the Open Folder button. 4. Quit Thunderbird. 5. In File Manager go up 3 levels, which should put you in C:/Users/username/AppData/Roaming 6. Copy the Thunderbird folder to a USB drive. 7. Insert the USB drive into the target computer. 8. Install Thunderbird on the target computer, then launch it. 9. Disregard creating a new account. Instead click the hamburger menu in the title bar, select Help, then Troubleshooting Information. 10. Scroll down to Profiles and click the Open Folder button. 11. Quit Thunderbird. 12. In File Manager go up 3 levels, which should put you in C:/Users/username/AppData/Roaming. 13. In File Manager click on the USB drive. You should see only a Thunderbird folder. Copy that in its entirety. 14. Click the Back arrow in File Manager to return to C:/Users/username/AppData/Roaming and paste the copied data from the USB drive. 15. Open Thunderbird. You should now see your email account. Check your message filters and address book to confirm that they've been imported.

I hope that these steps will help anyone that has trouble with the original instructions. Best of luck.

Your instructions are nearly correct but ambiguous. You do not mention removing the current Thunderbird folder - the one you want to replace. Also line 13 - Copy that in its entirety. Some people will think you mean to copy all it's contents, so it's best to state copy the 'Thunderbird' folder.

12. In File Manager go up 3 levels, which should put you in C:/Users/username/AppData/Roaming. 13. Delete the 'Thunderbird' folder because you want to replace it. (Alternative - when Windows says do you want to replace the Thunderbird folder you should say Yes.) 14. In File Manager click on the USB drive. You should see only a Thunderbird folder. Copy the 'Thunderbird' folder. 15. Click the Back arrow in File Manager to return to C:/Users/username/AppData/Roaming folder 16. paste the copied 'Thunderbird' folder from the USB drive into the 'Roaming' folder.

Those instructions are ok for some people, but many people are still going to go to the wrong place. You would not believe how many people paste the copied Thunderbird into the current Thunderbird and not into the 'Roaming' folder OR if they assumed you meant copy all the contents of the Thunderbird folder in it's entirely, then they paste all of them into the current Thunderbird folder and end up with tons of duplicates and loads of issues and the OS constantly asking if it's ok to overwrite - it can cause no end of confusion.

I would not have had people using the 'back in file manager' because they lose track of where they are supposed to be. In that situation it's best to access the usb and 'copy' the 'Thunderbird' folder first. Then access the the profile folder.

Some people find locating the Thunderbird folder via Thunderbird itself easy enough, but then forget to exit Thunderbird.

Sometimes people say they followed the instructions, but then you discover they did not do exactly as advised in the first place.