A catch-all email mailbox is one that captures all the emails sent to non-existent addresses. For example, if your email address is email@example.com, but someone 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 single 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per domain name can have this feature enabled and in this way you will never miss emails because the other party has an out-of-date address or has made a mistake. The negative aspect of setting up a catch-all mailbox is that you may start receiving plenty of junk emails, but this issue can be solved by using anti-spam filtering software. It’s also important to keep in mind that a mailbox with an activated catch-all feature cannot redirect inbound emails to a 3rd-party email address.