A catch-all mailbox is one that collects all the email messages sent to invalid addresses. For example, if your address is email@example.com, but somebody mistypes it and sends an email message to firstname.lastname@example.org, it will still be received in the catch-all mailbox that you have configured. Only one mailbox per domain can have this feature enabled and thus you will never miss emails because the other party has an out-of-date address or has made a mistake. The downside of using a catch-all mailbox is that you may start receiving a lot of junk email messages, but this problem can be fixed by using anti-spam filtering software. It is also vital to remember that a mailbox with an activated catch-all feature cannot forward incoming emails to a third-party email address.