A catch-all mailbox is one that captures all the messages sent to nonexistent addresses. For instance, if your email address is email@example.com, but someone 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. Just one single mailbox per domain can have this feature enabled and thus you will never miss messages because the other party has an outdated email address or has made a spelling error. The disadvantage of having a catch-all mailbox is that you may start receiving lots of spam email messages, but this issue can be solved by using anti-spam filtering software. It is also important to bear in mind that a mailbox with an activated catch-all functionality cannot forward inbound emails to a third-party email address.