One of the email options I offer to my clients is the ability to use what Google calls Google Apps which is a business version of their Gmail, Calendaring, and other various services. The GMAIL service offers the IMAP protocol to synchronize email with various mail clients (Outlook, IPhone, Web...). The benefit of IMAP is that you will have same version of your mail wherever you access it from.
One of the biggest hang-ups people have with using this is the whole paradigm of archiving messages vs. deleting messages. Using the IMAP interface the delete command is interpreted as Archive to delete a message you...