The Chapter Key Parts of the UNIX Filesystem explained how MH stores your messages: instead of keeping them all in the system mailbox or a big message file, MH keeps each message in a separate file. Once you start using MH, it takes a little work to move MH messages back to your old system. So if you've been reading electronic mail on your UNIX account before now and you're not sure that you want to use MH permanently, you may want to save your current email messages in a place where your current email system can find them.