I am not the one to guide you through this, as I know little of PST files and the like. But, on contacts, this addon may simplify the process:

https://addons.thunderbird.net/en-US/thunderbird/addon/outlook-address-book-enabler/   Although exporting and importing csv can work, but it's tricky getting the csv's in sync. IMAP is not a problem. Converting POP files to mbox is the major challenge.

Thanks for the reply. I'm not too worried about the account types (POP vs IMAP) since both work in tbird. The concern is if the migration tool also migrates accounts of both types, if at all.

I had hope somone with more expertise in Outlook would respond. I know the Thunderbird import feature supposedly requires that Outlook be installed on PC. The biggest challenge is converting POP and local files to mbox. There is a URL that may have tips here: https://www.syscurve.com/blog/how-to-import-outlook-to-thunderbird.html I am not saying that product works, but the URL does list several options, Good luck.

I was hoping that someone might have actual experience doing a migration from Outlook.

From what I've found so far, there are a dozen or so tools out there. This seems to be the best rated and most complete solution: https://www.systoolsgroup.com/outlook-to-mbox.html

This page gives detailed steps for converting PST to MBOX link text.

What I'm not sure of is once the conversion is complete, what is the best way to get those email accounts added to Tbird and "bound" to the MBOX files.

I'll keep researching.

Ok, I am not sure exactly what you want, but I'll offer this info for the mbox files. 0nce you have converted messages to mbox, there are two ways to place into Thunderbird. The target should be the Local Folders, as those are separate from account folders. Option !: - exit thunderbird - in windows file explorer, copy the mbox files to the Mail\Local Folders folder in the thunderbird profile - restart thunderbird and the folders should appear. NOTE: you can locate the profile by clicking help>troubleshootinginformaation, scroll down to 'profile folder' and click 'open folder'. That places you in profile. Click the Mail folder and then Local Folder will appear.

Option 2: - install the importexporttool NG addon - highlight Local Folders - rightclick and select importexport option to import mbox

Thanks for the info.

I've determined that I'll need to manually configure each account in tbird. For POP accounts I'll have to move the emails from local folders to the account folders. For IMAP accounts, I'll have to see what emails/folders download from the server and manually move the unsynchronized folders from local folders to the account.

Thanks again.

For POP accounts, Thunderbird will immediately attempt to download messages. If you have exported all the messages and then are none downloaded since the export, I encourage you to set up the POP account WITHOUT the password to avoid immediate downloads. Then use the importexport tool to import the input and sent mboxes to the account. That is intended to have the account primed prior to activating so that new messages will be added to the folder and avoid having to merge messages. That is doable, but extra steps.

For IMAP folders, click to account settings>synchronization&storage and click advanced button to specify which folders for download to PC. Thunderbird will automatically populate all folders.