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

It depends. If the account doesn't require an APP password, you may be safe. Do this to prepare for new PC: First, be sure your release of thunderbird is current and is the version you will use on new PC. Not mandatory, but can prevent unneeded problems. Then... 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 This copies all passwords. So, unless the account requires unique passwords per PC (e.g., gmail) then you'll be okay. I do strongly recommend checking account online and making a copy of your password. Thunderbird is often asked to restore lost passwords, and it cannot do that. You can see the password being used at settings>privacy&security.