A catch-all mailbox allows you to receive email sent to your domain that might be misaddressed or misspelled (for example, bob@ instead of robert@yourdomain.com). Any email messages addresses to a non-existent @yourdomain.com email address will be sent to the catchall inbox rather than "bouncing" or being returned to the sender.
By default, the catch-all is turned off. If you'd like to turn on the catch-all mailbox:
Email Control Panel: Additional Options Link
Email Control Panel: Additional Options Assign Catch-all Link
Assign Catch-all Dialog Box
Email Control Panel: Catch-all Assigned Message
For a Custom Mailbox account with one email address, the catch-all is assigned to the default email address. A Business Mail owner or administrator may designate any active email user's email address as the catch-all.
Note: Because a catch-all mailbox collects everything sent to your domain, it can accumulate spam. If you find you're receiving too much junk mail, turn off the catch-all.