I am new to Exchange2010 and have a question on CAS server.
I am trying to find the information about car server connectivity to mailbox server if they are in a  separate box.
How the cas server submit mail to mailbox server if it is on a separate box?
Does it use smtp connector to connect mailbox server?
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Suliman Abu KharroubIT Consultant Commented:
sara2000Author Commented:
I have been to this, outlook connect to car and mail submitted to hub transport.
Does the outlook communicate with hub transport or cas  communicate to hub, if so how does it communicate ?
Tim EdwardsIT Team Lead - Unified Communications & CollaborationCommented:
Here is a good quick description of the roles for exchange 2010 and how they work together.

Depending on your model you are looking to do all roles can run on a single server or you can put the cas/hub on one server and the mailbox on another server.

Depending on your mail client which sounds like outlook will connect to the cas, the hub handles all mail flow and the mailbox holds the databases and mailboxes.

I hope this is what you are looking for and it helps you
Suliman Abu KharroubIT Consultant Commented:
Clients connects to CAS, CAS authenticate and proxy the connection to Mailbox.

HT is used for inbound and outbound mail submissions.
Adam FarageEnterprise ArchCommented:
Well.. here is how Outlook connects into Exchange. To keep it short and simple, just to get Outlook to populate emails from the clients mailbox, you only need the CAS and Mailbox role.

Client opens Outlook, which then uses AutoDiscover to find the CAS. If the client is internal it will query the SCP from Active Directory (SeviceConnectionBinding) which will then resolve to the CAS or CAS Array. Outlook will then request the appropriate URL's for the services it requires (in this case the InternalURL for EWS) and then make its initial connection.

At first Outlook will send a RPC request over TCP 135 (RPC Endpoint Mapper) to find out the services TCP ports (Address Book Services, RPC Client Access and Public Folders if you have it). Once Outlook receives this request it utilizes the AuthN module to authenticate the user via Active Directory, and then also queries the Global Catalog Server to find the msExchangeHomeMDB, msExchangeVersion. Once it identifies the location, it gets the TCP ports requested by Outlook and sends it on its way back. Once Outlook receives it, it makes its connection and everyone is happy.

I might be confusing a few steps.. but that is how I remember it (but then again, I have yet to actually piece it all together in a while but looking at my notes that looks somewhat right).

The CAS does NOTHING (except for POP3 and IMAP) when it comes to mail submission.. nothing at all. That is all the HUB transport role.

When a client submits a new message it goes into either the Outbox (Outlook) or the Drafts (OWA) folder. A MAPI flag is raised on the mailbox, and the mailbox server queries AD for all available hub transport servers (called the "hub picker" services). Once a RANDOM HUB transport server is picked, the Mail Submission Service will then send an RPC request to the HUB transport server saying it has a message that needs to be picked up, and the HUB transport will then utilize the Store driver to pickup the message from the Mail Submission Service. Once it is picked up, the message is moved from either the Outbox or Drafts folder into the Sent folder. HUB transport processes the message (dont even ask me, there are a lot of steps) and then message goes outbound.

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