When I open up the mail app, my memory usage for the app starts at 2gb then 4gb then 29gb then 49gb before my computer freezes and is asking me to force quit.
TAHOE: MAIL APP: HUGE MEMORY LEAK
This is the developers forum.
Unless you suspect this is a bug, in which case I recommend you report it via the feedback app, I recommend you contact Apple Care if you need technical support.