A catch-all email mailbox is one that collects all the emails sent to inactive addresses. For instance, if your address is firstname.lastname@example.org, but somebody mistypes it and sends an email message to email@example.com, it will still be received in the catch-all mailbox that you have set up. Only one mailbox per domain can have this feature activated and in this way you will never miss emails because the other side has an obsolete address or has made a spelling mistake. The negative aspect of setting up a catch-all mailbox is that you may begin receiving lots of junk messages, but this problem can be fixed by using an anti-spam protection solution. It is also essential to remember that a mailbox with an enabled catch-all functionality cannot redirect inbound email messages to a 3rd-party email address.