transfering Mail to new computer

I currently have a 2017 iMac and will be purchasing a MacBook Pro when I decide on the configuration I want/need. After consulting several people, I have decided that when I get the new computer I don't want to use Migration Assistant to move my info to the new computer- too much unneeded stuff on my current computer. However, there are certain things I do want to transfer- some files and music. I think I know how to save and transfer most of what I want. But my concern is with Apple Mail. I would like to transfer all my Mail files (several years worth of emails) but am unsure how to do this. Any help/suggestions?