A catch-all e-mailbox is one that captures all the emails sent to nonexistent 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. Just one mailbox per domain can have this feature enabled and thus you’ll never miss messages because the other party has an obsolete address or has made a mistake. The downside of setting up a catch-all mailbox is that you may start receiving plenty of unsolicited bulk email messages, but this problem can be resolved using an anti-spam filtering solution. It’s also important to bear in mind that a mailbox with an enabled catch-all functionality cannot forward incoming emails to a 3rd-party address.