Moving Thunderbird Data to a New Computer | Thunderbird Profile or Email Backup

On your source computer
Connect a device for data transfer, either a local one such as a USB flash drive, or a remote storage drive.
Click the menu button Fx57Menu, then click Help and select Troubleshooting Information.
Locate the /”Profile Folder/” entry, then click Open Folder.
Your Thunderbird profile folder will open in Windows Explorer.
Close Thunderbird.
From your Thunderbird profile folder in Windows Explorer, go up three levels.
Right-click on the Thunderbird folder and select Copy.
Right-click the device you are using to transfer your data, then select Paste.
If you are using a local transfer device, remove it safely from the source computer.
Note: This step can also be used to create a backup of your Thunderbird profile folder.
On your destination computer
Connect the same transfer device you have used before to copy your Thunderbird profile folder from the source computer.
Right-click on the copy of the Thunderbird profile folder that you created on the transfer device, then select Copy.
Open Thunderbird (Close the account setup window if it appears.)
Click the menu button Fx57Menu, then click Help and select Troubleshooting Information.
Locate the /”Profile Folder/” entry, then click Open Folder.
Your Thunderbird profile folder will open in Windows Explorer.
Close Thunderbird.
From your Thunderbird profile folder in Windows Explorer, go up three levels.
Right-click inside the folder, then select Paste.
When prompted, choose to replace your current data.
An Alternative Method:
Hold down the Option key while pulling down /”Go/” on the Mac’s main menu. Select and open Library.
Within the Library is a Thunderbird folder, which can be copied/pasted or Shared (ie. right-click, Share, Airdrop if the receiving computer is in close proximity)
Ensure you already have the Thunderbird app installed on your receiving computer, but don’t open it to check messages. Go through the same process (Option key, Go, Library) and replace the empty (or old) Thunderbird folder on the receiving computer with the existing Thunderbird folder that contains all your current data.
Test Thunderbird on the receiving computer – it should look identical to your original on the sending computer and contain all the same messages. CAUTION: Do not open Thunderbird again on the original computer – unless you repeat the process in reverse to transfer the folder contents back to the original computer before opening the app. (If you forget, you can manually check one version against the other to ensure important messages are retained, but it’s messy and time consuming.)

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