I need to have a better understanding how email flows within 2010. I understand Hub handles all indside and outside mail, even if the mail is from one internal server to another internal server. I like to know how does CAS server plays the role in email flow. thanks

Here is a diagram: http://www.microsoft.com/downloads/en/details.aspx?FamilyID=6eb8c09a-6ea4-442a-9faa-de33265ceb84&displaylang=en Detailed Info: http://technet.microsoft.com/en-us/library/aa996349.aspx Understanding Transport Pipeline The CAS role doesnt interact directly with message flow.

Depending how detailed you want to know about how the CAS work but I would suggest get the Exchange 2010 Architecture Poster from the below link and go through it. If you want to know more than I would suggest the technet library link below. http://www.microsoft.com/downloads/en/details.aspx?familyid=cea0cf7e-d824-49bb-8924-39d66a5fb88e http://technet.microsoft.com/en-us/library/dd298114.aspx

CAS handles non-MAPI clients such as OWA, POP, IMAP, etc. Fore more information, please see: http://technet.microsoft.com/en-us/library/bb125134%28EXCHG.140%29.aspx.

thank you for your respond, but i have reviewd most of these links already. I just need a simple description how mail flow within exchange 2010. I understand in exch 2010, it also handles mapi connection. so if someone sends an email from one internal mailbox to another internal mailbox, does it go through CAS and then hub and reaches the other mail servier. OR does it hit the hub only? or does hit CAS only alan thanks

If you have one AD site, and you have MBX servers and HUB servers in the same AD site, then mail will be picked up from the Outbox from Outlook and submitted to the transport server. From here it will be routed to the ultimate destination (internal or external). Sukh

thank you for your respond, but i have reviewd most of these links already. I just need a simple description how mail flow within exchange 2010. I understand in exch 2010, it also handles mapi connection. so if someone sends an email from one internal mailbox to another internal mailbox, does it go through CAS and then hub and reaches the other mail servier. OR does it hit the hub only? or does hit CAS only alan thanks the CAS role is not part of the message flow in your scenario. Messages travel from MBX to Hub to MBX internally within the Exchange Org.

The CAS server is more for owa,oab, pop3, imap4, activesync, GAL lookup and authentication. As for routing emails as mentioned by Sukh and Andy it's the hub transport task.

It depending on the services that run on the Client Access server Services Used by a Client Access Server Please remember to click Mark as Answer on the post that helps you, and to click Unmark as Answer if a marked post does not actually answer your question. This can be beneficial to other community members reading the thread.

CAS handles non-MAPI clients such as OWA, POP, IMAP, etc. The CAS server is more for owa,oab, pop3, imap4, activesync, GAL lookup and authentication. In Exchange 2010, CAS now handles all interaction between clients and their email, including mailbox access via Outlook (regular old Outlook as opposed to Outlook Anywhere). So MAPI too.