A catch-all mailbox is one that collects all the messages sent to invalid addresses. For instance, if your email address is firstname.lastname@example.org, but somebody miswrites it and sends an email to email@example.com, it will still be received in the catch-all mailbox that you have created. Just one mailbox per domain can have this feature activated and thus you will never miss messages because the other side has an out-of-date email address or has made a mistake. The downside of configuring a catch-all mailbox is that you may begin receiving a lot of junk messages, but this issue can be rectified using anti-spam protection software. It’s also important to bear in mind that a mailbox with an activated catch-all feature cannot forward incoming messages to a 3rd-party mailbox.