A catch-all mailbox is one that captures all the messages sent to invalid addresses. For instance, if your email address is email@example.com, but someone miswrites it and sends a message 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per domain name can have this feature enabled and in this way you will never miss emails because the other party has an out-of-date email address or has made a mistake. The negative aspect of using a catch-all mailbox is that you may begin receiving a lot of unsolicited emails, but this issue can be resolved using an anti-spam filtering solution. It is also essential to bear in mind that a mailbox with an active catch-all functionality cannot redirect inbound emails to a 3rd-party email address.