Hi I had a query regarding Outlook connectivity I was hoping someone could help on. If I view the connections Outlook has to servers (CTRL, r. click Outlook icon in system tray), then I see multiple Exchange servers and also a Domain controller. The weird thing is, even if I am using Outlook Anywhere on the Internet, and am not on the LAN, the DC is still there. Does anyone know why Outlook needs to connect to a DC *and* multiple Exchange servers? I thought it would only need to connect to one Exchange server (the server defined in the profile) and that would be all? Also, when Outlook is first launched, what are the servers it initially connects to and in what order? Finally, is Autodiscover reliant on Outlook 2007 or Exchange 2007? Thanks!

Hi,The client always uses Global Catalog from one of your domain controllers and yes it could connect to multiple Exchange Servers at the same time.Regards,Zoltnhttp://www.clamagent.org - Free Antivirus for Exchange http://www.it-pro.hu http://emaildetektiv.hu

Hi ZoltanThanks for answering.So if it uses a GC directly, then why we do need to specify an Exchange server in the Outlook profile? Surely, it can get this info from the GC too?Any why would it need to connect to multiple Exch servers?

Hi, Now I would like to explain the Outlook logon process when connecting Exchange server: 1, First Outlook resolve the Exchange server in the Outlook profile to the IP address through DNS, then connect the End Point Mapper service (by default, EPM service listens on port 135) on the Exchange server. Next, Outlook would query EPM(End Point Mapper) service to get the port that Exchange DSProxy listens on. 2. Outlook connects and binding the Exchange DSProxy service on the Exchange server. After the session is established, Exchange will inform Outlook the proper Gloabl Controller it should connect to. 3. Outlook connects and binding to the Directory Store on the GC server. 4. After successfully authenticated on the GC, Outlook will then try to connect the EPM service (by default, port 135) on the Exchange server. Outlook would query this service to get the port that Exchange Information Store listens on. 5. After that, Outlook will successsful logon on the Exchange server.ThanksAllen

Hi Allen,Thanks for the excellent reply!Just a couple of questions - i) What does the End Point Mapper do exactly? I can't say I've heard of this? ii) Which GC will Outlook connect to, the one that the Exchange server is connected to or the closest one to the client?iii) On a LAN connection, if I check the Connection Status on the Outlook client, then the Directory servers (Domain Controller) is listed first, I assume this is not the order it connects to servers?iv) On an Outlook Anywhere connection, the Directory server *is* one of the mailbox servers, why is this?v) Again, in Connection Status, I can see multiple Exchange servers, why would Outlook need to speak to *multiple* Exchange servers? Again, thanks for the assistance here, really appreciate you answering my questions! :)

Hi,Sorry for the delay response.1, The Endpoint Mapper (EPM) assigns and resolves endpoints which listens to the 135 port. The services must register all available endpoints with the Endpoint Mapper service, such as RPC, Directory Service, Information Store. All that information are stored in a table in the Endpoint Mapper. WhenOutlook trying to connect Exchange server, it will send the query information to Endpoint Mapper in order to get the port of the relevant services.2, Outlook will use the same site GC (local domain preferred) as Exchange server. If that failed, it will use out of site GC. For example, consider the scenario where the client machine is in a different site to his Exchange server. The client's site has its own GC, but Exchange DSProxy will refer the client a GC in its own site. However, we can force Outlook to use the closest GC. You can set the registry to work on this issue.3, That's not the order.4, Please understand that the CAS or the Front-end server is responsible for proxying the HTTPS to RPC which is transmitted to GC. GC is internal machine which is not exposed to external user.5, That represent several sessions are running simultaneously.ThanksAllen

Excellent, thanks so much for the great explanations....really appreciate it.