Tier 1 support is absolutely clueless. All they know how to do is read from the support self help guide.
1) I need some help connecting an Outlook 2010 mail client to our comcast hosted mailboxes as Exchange, not pop or imap.
2) Because our domain server inside my building is the same name as the address for the Comcast mailboxes, the prescribed steps to connect as Exchange in the Comcast online "self help" guide do not work because the client can't find the mailbox on the server.
3) I need to know what server address I should use to have the Exchange client discover the users mail box.
If you are having any issues with making sure your Outlook is configured correctly for exchange:
1. Log into your Business Class Portal administrator account, then click on Email under Manage Services
2. Next click on the View DNS Info link and look specifically for your Domain Name addresses one of which is Exchange address. Please make sure that if you have brought in an existing Domain Name and you are looking for the Exchange address for that Domain Name. If you have any comcastbiz.net Domain Name then these addresses shouold be first in yoour View DNS Info list, then after this will be any Exisitng Domain Names that you brought in under the Comcast umbrella, if you will.
I believe the above aforementioned will answer you original post 1 & 2. For your original post 3, the autodiscover address is for your CNAME record as this link specifies and provides illustrative examples.