Where is account information stored for Mail (v10)

I am importing my mail accounts by hand as I want to have an absolute clean install. I found the mail boxes etc but can not find where mail has stored the information of my ISP accounts.

Meaning everything that normally shows up here:

I have imported the keychain files and the work fine everywhere else. So that part is covered. The mailboxes are not important as all accounts are empty (do not store mail on the computer). As you see they are POP accounts in case it matters.

I am Importing Mail from a MBP running 10.12 (Sierra) to the new one also running 10.12. There is a V4 and a V2 file in the mail folder (/Users/x/Library/Mail), and the V2 file has an Accounts.plist in the MailData folder, but is otherwise empty (previously moved direct from 10.9 to 10.12 so skipped the V3 bit).

Does anybody know how to do this, what file to move? Where does it hide this information?