Hi Let me explain the current architecture (Production Environment) : We have a Domain Controller ( Windows Server 2003 R2) (This is the primary DNS Server )+ Exchange Server ( Windows Server 2003 R2) which is also the additional Domain Controller ( Plus the Global Catalog Server) + the Schema Master Role is held by the Exchange Server (ADC)..Customer purchased two new powerful servers and wanted us to migrate the Domain Controllers and the Exchange Server onto these new boxes and discard the old servers.We started off by configuring one box as the Additional Domain Controller ( which would hold the Global Catalog) + DNS Server and replicated information over the network - Successfully completed Operating System : Windows Server 2008 R2 64 Bit.Seconf we installed Exchange Server ( Windows Server 2008 64 bit) on the Second Box after it was joined to the Domain and Installed CAS + Hub + Mailbox Server Roles onto the server. We then migrated all the MAilboxes to this new Exchange Server . We choose the option while moving for Domain Controller and Global Catalaog Server as the new Additional Domain Controller configured on Windows Server 2008 R2,Now my Question is if I move the 5 FMSO Roles through the dsa.msc and Active Dictory Domain and trusts to this new Additional Domain Controller can i remove the Old PDC from the exisiting architecture without any production Downtime ???I need to remove the Old Exchange Server also what are the necessary Steps to be taken ??Currently internet mail is routed through a Smart Host so do i have to redo the settings on the new Exchange Server ??KIndly Suggest

Yes you can move the FSMO without any downtime.Move the OAB to the new server, check that you have a new certificate for the new exchange server, if public folders move all the replicas to the new one, finally sure that you have move all the mailboxes. Since it is a Domain Controller maybe you need to do some prerequisites but i´m not sure what to do.Check if the send connector has the new hub transport server if yes...nothing to do..however the receive connector must be set to receive email from the firewall, apliance or the device that delivers email to exchange server...don´t forget relay applications..Hope this helpCapecolMCSA - MCTS Exchange Server 2007 - 2010Blog: http://capecol.spaces.live.com/default.aspx

(1) You can transfer all the FMSOs roles without down time. Make sure the new DC acts as an internal DNS and Global Catalog Server as well.(2) Necessary steps for removing the old Exchange Server 2003:Henrik Walther: Transitioning from Exchange 2000/2003 to Exchange Server 2007 (Part 1 through 3)http://www.msexchange.org/tutorials/Transitioning-Exchange-2000-2003-Exchange-Server-2007-Part1.htmlhttp://www.msexchange.org/tutorials/Transitioning-Exchange-2000-2003-Exchange-Server-2007-Part2.htmlhttp://www.msexchange.org/tutorials/Transitioning-Exchange-2000-2003-Exchange-Server-2007-Part3.html(3) SMTP Smart Host: Stick with it for now. See H. Walther: "In addition you should make sure that any Send Connectors under Organization Configuration > Hub Transport > Send Connector tab are configured so that they can send outbound mail (either using a smart host or DNS MX) properly" (See Figure 3.10 in part 3).Setting up an SPF record for your domain is also a good idea, especially if you relay messages off of your ISP: Sender ID Framework SPF Record Wizard http://www.microsoft.com/mscorp/safety/content/technologies/senderid/wizard/Before you consider to do away with your Smart Host, make sure the Reverse DNS lookup for your outbound SMTP IP address is not failing. Several of the larger companies do a revers DNS lookup before accepting your mail, such as Yahoo and COMCAST. The strictest requirements is AOL (at least explicitly to my knowledge):AOL SMTP Error Messageshttp://postmaster.aol.com/Postmaster.Errors.html#421dnsnr MCTS: Messaging | MCSE: S+M | Small Business Specialist