Copy the msgFilterRules.dat file from one account to another:

http://kb.mozillazine.org/Filters_(Thunderbird)#Export.2FImport

Help/Troubleshooting Information, click Open Folder to open the profile folder in Explorer, close TB, copy or edit the files.

Thanks for the help and the link - that led to me being able to solve the problem, but the location of the file was unclear, or has changed. After a little hunting, I found it is at C:/Users/[my user dir]/AppData/Roaming/Thunderbird/Profiles/xc91cy0h.default/ImapMail/[my imap server name], in the case of a Windows installation. (I am guessing the xc91cy0h.default directory name is generated and probably different for each installation, and the ImapMail directory is called something like PopMail or whatever, for different mechanisms.)

I was able to edit and merge the one rule I actually already had with the others I copied, but beware using Excel to do this - it inserted extra quotes on each line. Better to use a text editor.

Hi, I tried this and the rules show up under my other email, but none of the folders into which the specified emails should be moved show up. I've compared the copied version (with updated email address) to my original, and can't figure out why the new on isn't working. I tried creating a new filter to see how it got formatted, copied that format to the others filter rules, but no joy. Am I going to have to manually re enter every target folder?

Any suggestions on what I'm missing?

Copying a set of filters from one account to another doesn't copy the folders that the filters refer to - you have to create the folders manually. Unless I misunderstand your question. The only time this would be unnecessary is if the folders are the same, independent of the account, e.g. subfolders of Local Folders.

Hi, I copied all the folders from the old email address to the new email address before doing the message filter file update. So all the folders are there, but the message filter file doesn't seem to recognize that fact.

I would open the msgFilterRules.dat file in a text editor and see if you can find any reason why the filter is not recognizing the folders. You can also activate the Filter Log in the Tools/Message Filters window.

Um, yes, and I discovered a user error. One can't substitute "/" for "." and have things work, lol! Thanks for nudging me to take a closer look. Once I fixed that, all worked as designed.