* abook.mab and history.mab - Personal Address Book and Collected Addresses.
* cert8.db - Security certificates
* key3.db and (number).s - Saved passwords.
If you do not migrate the prefs.js file, use about:config to modify the signon.SignonFileName preference value to match the copied (number).s file name.
I was unable to follow this last part. There is no signon.SignonFileName that i can find.
* mimeTypes.rdf - Actions to perform on downloaded files
* msgFilterRules.dat (in each account subfolder) - Message filters
These last one appears inside the mail folder which I copied completely.
* popstate.dat (inside each POP mail account subfolder) - Keeps track of which messages have been downloaded from the POP server. If you don't copy it, previously downloaded messages still on the server might all get downloaded again.
This last one is inside mail folder.
* training.dat - Custom training for Junk Mail Controls
* Mail and ImapMail folders - E-mail messages and settings.
I copied the mail folder, Comcast.net uses POP.
After doing all this when i open Thunderbird--I get a set up wizard. No accounts are there. No folders are there.