A catch-all email mailbox is one that gathers all the messages sent to nonexistent addresses. For example, if your email address is email@example.com, but somebody misspells it and sends an email message to firstname.lastname@example.org, it will still be received in the catch-all mailbox that you have created. Only one mailbox per domain can have this feature enabled 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 having a catch-all mailbox is that you may begin receiving a lot of unsolicited bulk emails, but this problem can be solved using anti-spam protection software. It is also important to bear in mind that a mailbox with an enabled catch-all feature cannot redirect incoming messages to a third-party address.