A catch-all mailbox is one that captures all the emails sent to nonexistent addresses. For instance, if your email address is firstname.lastname@example.org, but someone miswrites it and sends an email to email@example.com, it will still be received in the catch-all mailbox that you have created. Only one single mailbox per domain name can have this feature enabled and thus you will never miss emails because the other side has an outdated address or has made a typographical error. The downside of creating a catch-all mailbox is that you may start receiving lots of junk messages, but this issue can be resolved by using an anti-spam filtering solution. It is also essential to remember that a mailbox with an activated catch-all feature cannot redirect inbound messages to a 3rd-party email address.