Set a Catch-all Address
If an email is sent to an address that has no mailbox or forwarding address, by default it will be bounced back to the sender (which is the preferred behavior for most as Mailboxes and forwarders can be set up for all email addresses that are required).
A catch-all (wildcard) address can be setup so that email's that do not have a Mailbox or forwarder associated with them, can be received by the catch-all email address.
Steps to Setup a catch-all address
Follow the steps below to set up the catch-all address for a domain:
From the list of mail domains, select the domain that the you would like to set up the catch-all address.
Select the "Domain settings" option.
Under the "Catch-all address" field, select the option "Forward messages to:". (see Figure 1)
Type in the full email address that you want the messages sent to. This email address can be any valid email.
Click "Save changes" to set the catch-all.
The catch-all can also be disabled by selecting "Bounce the Message".