Embarq Corporation was the largest independent local exchange carrier in the U.S. before its acquisition by CenturyTel in 2009, which later rebranded as CenturyLink. The document provides a step-by-step guide on how to block an email address in EmbarqMail through CenturyLink's website. Users can create a filter by entering the email address they wish to block and setting its action to 'discard.'