Export emails from stock email client

A

AC Question

The phone (not rooted) is running Lollypop (5.1.1) and the stock email version 8.0 and has nearly 7000 emails that have been pulled down with pop3. The emails are no longer on the server.

I am looking at a way to get these emails off the phone and into a format that I can use elsewhere. The owner of these emails wants them on Outlook ultimately, but I am open to any method such as transfer to IMAP, or import into Thunderbird just to access them off the phone.

I have tried installing an IMAP account alongside, but when trying to move emails I get the message POP emails cannot be moved. I also thought of backing up, but I cannot access the data directory.

Any ideas? Thanks