After messing around with lots of fun configuration, I think my email system is working properly. I'm using a combination of Postfix, Dovecot, MySQL, RoundCube, and OpenLDAP to provide email services for johnwoltman.com. This lets me use a better webmail client than 1and1's craptastic "WebMail 2.0," and I can do do away with quotas because there's so few actual mailboxes.
The OpenLDAP integrates with my OS X/iPhone address book (and Jen's too!), so we have all our contacts wherever we go.