A catch-all e-mailbox is one that captures all the messages sent to non-existent addresses. For instance, if your email address is email@example.com, but somebody mistypes it and sends an email to firstname.lastname@example.org, 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per domain can have this feature activated and in this way you will never miss emails because the other party has an out-of-date address or has made a spelling mistake. The downside of configuring a catch-all mailbox is that you may start receiving a lot of spam email messages, but this issue can be solved by using an anti-spam protection solution. It is also important to bear in mind that a mailbox with an activated catch-all feature cannot forward incoming email messages to a third-party email address.