If you answered "one", I'm here to tell you you're setting yourself up for a
lot of spam, viruses, abuse and who knows what else. Heck, if you answered
"two", there's still room for improvement.
Yes, I believe that anyone who uses email extensively (and who on the
internet doesn't these days?) needs at least three separate email addresses.
Perhaps even three separate email accounts. Accounts and addresses are
most definitely not the same, and I'll explain why that's important in a
moment.
In my opinion, the days of using just a single email address are long past.
Fortunately ISPs are getting wise to this as well, and with the plethora of
free email services, it's easy to have a virtually unlimited number of email
addresses. If you happen to own your own domain, then the possibilities are
virtually endless.
But why would you want more than one? And assuming you have more than one,
how should they best be set up?