An SMTP Dropbox is basically insurance for your e-mail. If you run your own mail server and it isn't available for some reason there's a good chance you will lose e-mail. When your server isn't available an SMTP Dropbox will store all mail meant for you until your server comes back online, then it will pass that mail through. So you don't lose your e-mail.

Set-up $29.95 Monthly $20.09