Transferring v5 mail to v7 (high sierra to catalina)
What is the best process to transfer a massive amount of emails/mailboxes from High Sierra (10.13.3) Apple Mail to Catalina?
I've read migration assistant is horrible, "export mailboxes" doesn't work, and that transferring the v5 folder to the v7 may work (but no confirmation).
If I transfer v5 to v7, do I move the contents from one to the other? Or do I just copy over v5 and see what Mail does with it?
MacBook Pro 13″, macOS 10.15