The importexport addon can extract all messages per folder in eml format. You could then copy them all to a USB.

Thanks, I have that add-on installed but have yet to try it. I assume if I "export" emails from a folder to a USB I can import them to a different TBird install on a different PC? Would copying and replacing the global-messages-db.sqlite file on the other PC work too?

The importexport addon can extract and also import.

Thanks, I have that add-on installed but have yet to try it. I assume if I "export" emails from a folder to a USB I can import them to a different TBird install on a different PC? Would copying and replacing the global-messages-db.sqlite file on the other PC work too?

The sqlite file is not needed for this operation, and neither is an add-on. Select the messages in the folder (Ctrl+A to select all), then Ctrl+S to save them as eml files in an external File Explorer folder. To import them to another PC that has TB, create a subfolder of Local Folders, then add the eml files to the subfolder by drag and drop from File Explorer.

I wanted to copy all emails from ALL folders so I copied the global-messages-db.sqlite file and replaced the existing one and there they were, all files in all their respective folders. It was a piece of cake. Now I need to copy my calendars over.

When you open a message, does it show any content?

When I replaced the sqlite file with the one I copied, ALL of the emails were there, in ALL of their respective folders. Every one I open is correct with all original content. Easy Peasy, eh?

The importexport addon can extract all messages per folder in eml format. You could then copy them all to a USB.

I did not want to bother dealing with individual email file and flders, too messy. I have thousands of them due to businesses, forums, groups etc that I own or manage. All I had to do was to copy and paste ONE file. Maybe others who want to do the same, they will try it to validate what I did.