A catch-all email mailbox is one that captures all the emails sent to non-existent email addresses. For instance, if your email address is email@example.com, but someone misspells it and sends a message to firstname.lastname@example.org, it will still be received in the catch-all mailbox that you have created. Just one single mailbox per domain can have this feature activated and in this way you will never miss messages because the other side has an outdated email address or has made a typographical error. The negative aspect of having a catch-all mailbox is that you may begin receiving lots of unsolicited email messages, but this issue can be rectified by using an anti-spam filtering solution. It is also vital to remember that a mailbox with an activated catch-all functionality cannot redirect incoming emails to a 3rd-party address.