On a shared hosting system, each POP box username must be a unique name. If you are attempting to create a POP box and you receive the message that the POP box "is not available", there is an easy fix.

Simply create another form of the name you desire, such as sales03 instead of sales, and then setup an email alias for email to sales@yourdomain.com to go to the POP box sales03.

In your email program (such as Outlook or Eudora), you can still set the email address to sales@yourdomain.com, but you would set the Account Login / Username to sales03 using the example above.