A catch-all e-mailbox is one that collects all the emails sent to invalid email addresses. For instance, if your 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 configured. Only one single mailbox per domain name can have this feature activated and in this way you will never miss messages because the other party has an obsolete email address or has made a mistake. The negative aspect of using a catch-all mailbox is that you may start receiving lots of junk email messages, but this issue can be rectified by using an anti-spam filtering solution. It is also essential to keep in mind that a mailbox with an active catch-all functionality cannot redirect incoming emails to a third-party email address.