A catch-all mailbox is one that gathers all the email messages sent to invalid addresses. For example, if your email address is firstname.lastname@example.org, but someone misspells it and sends an email message to email@example.com, it will still be received in the catch-all mailbox that you have configured. Only one mailbox per domain can have this feature activated and thus you will never miss emails because the other party has an outdated address or has made a spelling error. The downside of using a catch-all mailbox is that you may begin receiving a lot of unsolicited messages, but this issue can be rectified using anti-spam filtering software. It is also essential to keep in mind that a mailbox with an activated catch-all feature cannot forward incoming messages to a 3rd-party mailbox.