A catchall email account allows mail sent to any non-specified mailname at your domain to be dealt with in a particular way determined by you. You can use this as a global mail drop or as a means of bouncing unwanted email.
To send all unresolved email to a catchall email address:
1) Log in to your control panel.
2) In the Mail section, click on Default Address
3) You will see several options. Primarily, you can either reject the mail (ie send a bounce message for a non-existent account), or set it to "Forward to email address:", then enter the address where all unresolved email should go. You can enter either one of your domain's POP3 or email redirects or an outside email address.
4) Click on Change when done
If you prefer to force all unresolved email to bounce back with a specific message, in step 3 above instead check the radio button for "Discard with error to sender" and enter the text that you want to appear when the message bounces.
Any mailnames you create will not be affected by these changes - they apply only to unspecified (unresolved) mailnames.
Note: In most cases we will turn the catchall off by default when we first set up your hosting plan. This will mean emails will bounce except for any specifically set up. This can be changed by you at any time. Continued use of the catchall is not recommended however as it can also result in catching lots of spam and if used as a forward to an external domain can result in you being blacklisted as a spammer yourself. We recommend that catchalls be used only in specific circumstances and only for limited periods.