This article explains how to setup Microsoft Outlook or Other Third Party Mail Clients to use with Email Defense
By default, connecting via POP, Microsoft Outlook will work with the default configuration. On the other hand using IMAP you will need to manually configure Outlook or other third-party mail clients with the hostname as mail.<insert your domain here>.
By default on an IMAP configuration Microsoft Outlook and possibly other mail clients will attempt to connect to pop.myhostcenter.com and smtp.hostmycenter.com, if you get a user password prompt with the information previously provided, please cancel this dialog and manually enter your mail host name: mail.<insert your domain here>.
If you need further assistance with this please follow along in the KB articles listed below: