You may be in for fun time as the way OSX describes files names and paths id different to windows. Unfortunately your attempts to fix you problem appear to have made them much worse.

There is one glimmer of hope. In Thunderbird open the troubleshooting information on thee help menu. Click the show profile button. OSX should now open into the currently being used profile folder.

SO now close Thunderbird and copy your original profile folder into the profile folder being used. This should generate messages about replacing files such as abook.mab if you are copying over the correct things.

Now restart Thunderbird and report what you see. Partial data is sort of half expected. Especially if you have set the folder locations for any of your accounts.

Matt, Thanks for your insight! You are quite correct about my experience with Windows (DOS decades ago) fouling me up because of my ignorance of OSX. Curiously I tried to get fundamental help from Apple Support in how to get around the "trees," paths, and files, etc and they were of NO help. The first program I migrated from the PC was Thunderbird and I thought I was familiar with it, but when it came to OSX I had no clue. Yesterday in despair, I downloaded Quicken (which I was afraid would be a monster) and it was a piece of cake and I figured out from Quicken a major mistake with Thunderbird. To download the program to OSX you have to click and drag the big bird into Applications! Duh! It was NOT obvious as it was in Quicken with big arrows pointing to drag the big "Q" into the "A" for Applications. Thunderbird is OPEN and configured, BUT the 500 Mb of "In" messages are NOT present--only a couple that showed today, although a careful check of my profile shows the data (they say they are Unix executable). Any suggestions how to get all my data into the 2 mail accounts I setup EXACTLY the way they are in my PC??? Chuck

Matt, I have a "clue" as to why my old data does not show in Thunderbird.

In analyzing my profile (yes, I got that correct), I see there are 2 Mail folders! #One (the old one with thousands of emails) is indented 2 spaces to right on careful analysis and #Two (holds new data with a few emails) is indented only one space. Therefor the two folders with same name are not within the same hierarchy--very odd.

This is a bit of a conundrum and will listen to your suggestions before wrecking what is already set up! Chuck

in an attempt to not make things worse, left try the following.

Copy the old mail folder (double indented) in it's entirety into the new mail folder.

Here we have a couple of choices. One is brash, the other conservative and the way I suggest first.

Open the local folders "folder" in the new mail nest and paste the old mail data in the the "local folders" folder

When you open Thunderbird you should have.

Local Folders
        └ Mail
          └ "Your old mail data"

The more brash method is to simple paste the "old" mail data over the "new" mail data. This will place things where you might expect to find them, but only is the account information that was in the original prefs.js file has made the leap. (given you have a copy of your old data, blowing the new away and starting again should not be a huge problem, if pasting over the existing does not work (it will replace what is in the new hierarchy, is why it is somewhat brash.)

Either of those methods should work for you. But I will leave it to you to choose, based on knowing the risks.

Matt, You had a great pair of final solutions and I chose the "brash" solution because I had very few emails to preserve in the new MacOS system (only 3 in my account and 2 in my wife's email account that I wished to save on the new program) so I went for it to "look and act correctly." Your email was one I wanted to keep and I just forwarded out of the old PC to the Mac.

I feel far more confident now of MacOS and I am very glad I did not give up, but I was close. I have loved Thunderbird since before it transitioned from Netscape and I know exactly where Mozilla headquarters are in Mtn. View since I lived in Menlo Park and worked in Los Altos and now retired in Port Angeles, WA. Thanks so much for your wise help! Chuck