How do I get ALL my mail?

I'm using a MacBook Pro M4 with Sequoia 15.6.1. Mail won't download all my mail from Earthlink. I don't see any pattern, but it does seem to ignore everything related to Constant Contact. I would like to get it all. I tried selecting Rebuild, which cleared my local mailbox, but then downloaded nothing from Earthlink. There are about 60 messages available. How do I get them all?