Hi All, Can someone please expaln me how internal mail flow happen in Exchange 2010. Appriciate if you could explain from basic such as start from Outbox of outlook to Exchange server (HT, CAS & MBX). In my Current scanario we have two Physical sites Site A and Site B and below roles: Site A: Production 2 MBX server 2 CAS & Hub servers (each server combined with CAS & HUB, also configured with NLB) 1 SMTP (DMZ) Site B: DR 1 MBX server 2 CAS & Hub servers (each server combined with CAS & HUB, also configured with NLB) 1 SMTP (DMZ) Both PR and DR MBX servers are configured with DAG Technology. Regards, Muniraj

Mail is transferred from the client to the Client Access/Hub Transport server. It is then moved to the closest Hub Transport server for delivery to the mailbox server. That is it. The Outlook client then collects it from the mailbox, via the CAS role. Simon. Simon Butler, Exchange MVP Blog | Exchange Resources | In the UK? Hire Me.

Simon, Actually I was looking into still deeper level. While googling last night i found it out. Here it is........ Outbox is a sychrionized folder in the mailbox and does not exist only on the Outlook client. When a message is placed in the senders Outbox, the Microsoft Exchange Mail Submission service who monitor the mailboxes regulerly, alerts the store driver, which retrieves the message from the senders Outbox. The store driver then places the messages into the Submission queue on a Hub Transport server, this can be any hub transport server in the same Active Directory site as the mailbox from which the message was retrieved. The Categorizer then pick up one message at a time from the Submission queue, processes it against recipient resolution and content etc. and then places it in a delivery queue. If the recipient resides in a local mailbox server it is placed in a mailbox delivery queue, the delivery queue delivers the message to a local mailbox by using the store driver. If the recipient is on a remote server the a remote delivery queue delivers the message through a Send connector. Here is a step by step description of the process: 1. Microsoft Exchange Mail Submission service - Notifies a Hub Transport server role in the local Active Directory site when a message is available for retrieval from a senders Outbox 2. Store driver - Retrieves messages from senders Outbox 4. Submission queue - Stores all messages on disk until processed 5. Categorizer - Processes one message at a time from the Submission queue 6. Store driver & Send connecotor - Delivers the message to user mailbox if the mailbox is withing the site or in case if it is on remote server delivers the message through a Send connector. Regards, Muniraj

hi, Yes, like you said. Here is a picture that also describes the mail flow. Note: exchange 2010 outlook 2010 connect CAS server with mapi/rpc not MBX server hope can help you thanks,CastinLu TechNet Community Support