Copy the contents of ~/Library/Mail/ and the mail preferences file ~/Library/Preferences/com.apple.mail to the same locations on the other Mac.
Just for clarification… I moved com.apple.mail.plist since that was the only thing in there that resembled com.apple.mail
Yep, that worked!
I moved com.apple.mail.plist since that was the only thing in there that resembled com.apple.mail