The important thing is the email account itself and whether POP or IMAP.

David - I don't understand your reply. Please explain how your reply relates to my inquiries 1,2, or 3. Thanks.

WLM is an email client. Such clients tie a PC to an email account. The email account is something you've set up, such as with Gmail, Outlook, or whatever. Possibly sharing the text to the right of the @ sign in your email account may provide that information. In summary, switching to a different client requires awareness of the current client's connection information.

OK, let me provide some more information to clarify.

My Thunderbird on my new computer is now connected to my email account. My email account is verizon.net. Quite some time ago verizon.net was taken over by AOL but the email accounts stayed as verizon.net

Here's my issue (which I suppose I could have made clearer at the start). On my old computer I have a ton of old emails stored in my Windows Live Mail THAT ARE NO LONGER IN MY verizon.net/AOL account. Those old emails are in various folders and subfolders in WLM on my old computer. I want to move those old emails into the Thunderbird I set up on my new computer.

Please let me know if you understand my request. Thanks.

Okay. The Verizon account transition will be transparent if IMAP (accessed directly on server). Otherwise, the mail folders need to be manually copied. A website with nice pictures on this is here: https://pcdots.com/blog/import-windows-live-mail-to-thunderbird-account/ summarizing the manual steps of exporting mail from WLM and rebuilding the folder structure in Thunderbird.

This other URL - https://support.mozilla.org/en-US/kb/switching-thunderbird#w_switching-from-windows-mail-or-windows-live-mail-to-thunderbird provides info on converting the addressbook.

The above steps would also apply to the old AOL messages. In this case, the approach would be to create new folders in the 'Local Folders' section of Thunderbird and build the message folders there.

I encourage reviewing the URLs a few times to get the mechanics. The addon, importexport, is needed to make this happen.

David - Thanks. I'll definitely study the links you provided.

Quick terminology question. When the term 'export' is used for mail messages does that mean the messages are cut and then taken away or are they copied for exportation? That is, after exporting do the messages still stay at the original location?

Good question. Someone else just asked that same question an hour or so ago. Export just makes a copy; the original stays where it was.

I just installed Thunderbird 115.2.0 on my Windows 7 computer. I want to transfer all my old mail from Windows Live Mail to Thunderbird before I get a new computer. I saw several posts you wrote about this so here's my question: The add-on's that enable moving windows live mail messages and contacts to Thunderbird are not compatible with the latest version of Thunderbird. Can you suggest another method? Do I need to install an older version of Thunderbird, then migrate my live mail data, then upgrade to the latest version of Thunderbird? I'm medium techy.

Since you know what addons you need, I suggest the easy approach would be to start with 102.15 (assuming that edition supports the addons you want) . It is at https://ftp.mozilla.org/pub/thunderbird/releases/102.15.0/