Filters for each account are in a file called msgfilterrules.dat If all else is the same, try copying from one profile to the other. These are text-editable so it's easy to view. And, if the 38gb is for IMAP accounts, do this. - exit thunderbird - locate the imap accounts in profile and delete the message folders - thunderbird will repopulate on new pc - now continue with these steps to copy profile

Here is the link for moving a profile in Windows when installed in default location:

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

Thank you David, that worked perfectly. saved me a lot of time. Just need to do it on my other accounts now. They are much smaller with only a few filters on each. Peter

You're very welcome.

I am running current software for windows and Thunderbird. I have two pcs in two locations. I want to merge the filters. Can i just cut and paste the filters into one file? If so, where in the dat file should I start the cut? Thank you

I have never tried that.I suggest creating two filters on one PC and then evaluating how the two are separated within the msgfiltsrules.dat file.That should give you the insight, if possible, on how to merge two filters.