I wasn't saying that importing the POP emails would mark them as read. I was saying that using POP at all does not communicate read status.

I'm still not convinced that when you had all three accounts set up, and checked the email in your sublables on account A, then went back to account A on your computer, the read status was not conveyed. That wouldn't happen. You're sure you weren't reading the email on account B, then seeing it still unread on your computer in account A? Because it doesn't matter how you add account B on your Android phone. There's no possible way for you to add it and make account A - on your phone or computer - reflect the read status.

Anyway, I'm glad I could help