https://support.mozilla.org/en-US/kb/moving-thunderbird-data-to-a-new-computer

If you want to move all accounts, settings, and messages it's easiest to just transfer the full profile. : Here is the link for moving a profile in Windows when installed in default location: https://support.mozilla.org/en-US/kb/moving-thunderbird-data-to-a-new-computer here is the info in brief steps: # ensure thunderbird is NOT running on old machine # enter %appdata% in search window on task bar and press Enter key # this should open windows file explorer in Appdata\roaming folder # highlight the Thunderbird folder and copy to external media # ensure thunderbird is installed on second computer and NOT running # enter %appdata% in search window on task bar and press Enter key # you should be in Appdata\roaming folder , copy&paste the exported Thunderbird folder there. This may prompt to overwrite an existing folder of same name. allow it # start thunderbird and all should be there If you just want to move some messages, I suggest exiting thunderbird and copying message folders (ignoring the msf entries) from within profile folder and pasting in the Mail\Local Folders folder of the receiving PC. If you need more detail, let me know.