I have my own server. Have had for many years, in fact. One of the early things I did with it was setup an IMAP server. Best thing I ever did with my email. (And the second best thing I did was setup a webmail service.) Desktops have come and gone, been upgraded, re-installed, email clients changed several times. Never lost any email. And the Maildir format on the server is extremely easy and robust to move to a new server, as has been done a few times, too.
Wade.