Can I copy two profiles on reinstallation

Solution 1:

Mails in Thunderbird are stored in mbox formatted files in your user profile. These mbox files are text files formatted in a special way, and they have no file extension.

You could copy the relevant mail files from your Windows installation, rename them with a name not yet existing in your Thunderbird account under Linux, and move them there. In Thunderbird, they will show up as new folders that have the name you gave to the mbox file. You can access and organize that mail in these folders.

This makes sense for locally stored mail only. For IMAP mail, just connect to the server to retrieve the mail stored on the server.

Local mail is stored under /home/<yourlogin>/.thunderbird/<random string>.default-release/Mail/Local Folders. Unnamed files with the names of your folders are the mbox files. They are accompagnied by a similarly named .msf file. This is an index file that automatically will be recreated by Thunderbird if it does not exist. Thus, there is no need to copy these.