Unable to connect Outlook 2013 via Exchange sync.

Hello efficient1 and welcome,

First thing you need to do is to make sure that your computer Outlook account is using the correct domain addresses. These can be obtained by logging into you Business Class Portal administrator email account. Then under Manage Services click Email, then View DNS Info.  This will provide you are list of all domains and all addresses associated to each domain.

After you obtain the domain addresses, then go back into you computer Outlook and make sure that you incoming, outgoing, Exchange email addresses correspond to those founf in your View DND Info list.

Hope this helps you out.