A catch-all mailbox is one that gathers all the messages sent to non-existent addresses. For example, if your 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 configured. Only one single mailbox per domain name can have this feature activated and in this way you’ll never miss emails because the other side has an outdated address or has made a mistake. The negative aspect of creating a catch-all mailbox is that you may start receiving lots of junk messages, but this problem can be fixed using anti-spam filtering software. It is also important to bear in mind that a mailbox with an activated catch-all functionality cannot forward incoming email messages to a third-party address.