A catch-all email mailbox is one that captures all the emails sent to nonexistent addresses. For instance, if your 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per domain can have this feature enabled and in this way you will never miss emails because the other party has an out-of-date email address or has made a spelling mistake. The drawback of setting up a catch-all mailbox is that you may start receiving a lot of unsolicited bulk emails, but this issue can be fixed by using an anti-spam filtering solution. It is also crucial to keep in mind that a mailbox with an enabled catch-all feature cannot redirect incoming emails to a 3rd-party mailbox.