The default mail account setting, also known as the catchall account, will direct all incoming e-mail (that does not have a popmail account or forwarder/alias set for it already) to the user or address you specify. By default, this setting is set to go to the main inbox for each cpanel account. When you change this to something other than the cpanel account's main username, please make sure to use a FULL e- mail address (EX: username@domain.com). For example if you wish to forward all mail for that domain (that didn't arleady have its own popmail box or forward elsewhere) to a popmail box you created on your account called mybox@domain.com, you would put mybox@domain.com into the textbox for the default mail account setting.
Q: Why wouldn't I want to put just mybox instead of mybox@domain.com?
A: Because when you just put mybox, exim (the mailserver) will attempt to deliver to the cpanel user with that username. If there isn't one, then the mail will bounce. If there is one, someone else could be getting your e-mail.
