A catch-all mailbox is one that collects all the emails sent to nonexistent email addresses. For example, 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mailbox per domain can have this feature activated and thus you will never miss messages because the other party has an out-of-date email address or has made a typo. The disadvantage of setting up a catch-all mailbox is that you may begin receiving a lot of spam emails, but this problem can be resolved using anti-spam protection software. It is also vital to know that a mailbox with an activated catch-all feature cannot forward inbound emails to a 3rd-party mailbox.