I too have a large ¡°documents directory¡± of emails I have saved in Apple mail. If if viewed one a day it would take me forever. Some of these mailboxes go four levels or more! I do ocassionally try and clear out a mailbox when I realize that that ¡°event¡± is over.
I wish there was an app that I could transfer my mail documents (Mailboxes) to That way I would probably do so once a year.
I am an officer in a number of groups I belong to and I am amazed howoften I need to refer to previous emails (received or sent) to answer some members question - prove I sent them a message, etc.