Optimize Outlook on Exchange

Configure Outlook for improved performance

Microsoft Exchange Server 5.5 has several components you can use to improveclient, server, and networking performance. You can optimally configureMicrosoft Outlook 8.03 to interact with Exchange by using the same techniques you used to optimize previous versions of Outlook and the Exchange client.

Optimizing network communications improves Outlook's startup time. If you misconfigure the client, it might have trouble locating the Exchange server. Two networking configuration areas you need to control are the network binding order and name resolution order. You can also optimize performance if you configure optimal address storage, message storage, and message archival.

Outlook Client Connections
When Outlook needs to communicate with the Exchange server, it establishes aremote procedure call (RPC) connection to the server, based on the RPC bindingorder you specify in the Registry. Depending on your Exchange and Outlookconfiguration and how you use the client, Outlook might frequently establishsuch a connection. An Outlook client connects to an Exchange server when Outlookstarts up, connects to your mailbox, opens another person's special folder, andviews Microsoft Schedule+ information or public folders.

When Outlook starts up or views special folders, it establishes connectionsto the Exchange server's private information store. Outlook identifies theExchange server to connect to from your home server. Your user profile specifiesthis server. After you connect to your private information store, Outlookestablishes a session to your home server and then uses that session for futurecommunication.

Another user might give you access to a special folder. To view the folder,you must establish an RPC connection to the user's home server (which might alsobe your server). Select File, Open Special Folder, Exchange Server Folder.Specify the user's name and the folder to view.

A special public folder stores the Microsoft Schedule+ free and busyinformation. By default, the first server in a site contains the free and busytime for users in the site. When you invite users to a calendar-requestedmeeting, the calendar automatically connects to the public folder to retrievefree and busy information. If your home Exchange server doesn't house the freeand busy public folder, Outlook establishes an RPC connection to the server inyour site to get the free and busy information.

Multiple servers in a site can house public folders. As with the free andbusy information folder, the client establishes an RPC connection to the serverthat contains the requested public folder. Large Exchange organizations withmultiple sites can replicate public folders to all sites for easy access.

A client might have access only to public folders in another site. In thissituation, Exchange uses public folder site affinity to inform the client whichsites contain public folder servers and what order to use in connecting to them(based on affinity value). If the requested public folder is not on a server inthe client's site, the client connects to other Exchange sites, in order ofaffinity, to look for the folder. A client might have to connect to multipleExchange servers in the site before it finds the requested folder. Thus, a quickRPC connection between the client and Exchange servers is important.

RPC Binding Order
To connect to the Exchange server from Outlook, you must first find theserver. This process involves checking the available network paths and resolvingthe server name. Outlook uses RPCs to communicate with the Exchange server. TheRPC binding order determines the order in which networking protocols andapplications protocols search for the server. Networks use multiple protocolsand network programming interfaces. Outlook is network independent, so itmethodically searches for the server on the network interfaces. The RPC bindingorder on the network interface is specific to Outlook and Exchange and is notrelated to the network binding order in Control Panel.

When an Outlook client communicates with an Exchange server, it uses theRPC binding order identified in the Registry to determine the appropriateprotocol and interface for connecting to the server. Table 1 lists availabletransports.

The default binding order for a Windows NT or Windows 95 client is ncalrpc,ncacn_ip_tcp, ncacn_spx, ncacn_np, netbios, ncacn_vns_spp. The Outlook clientattempts to use the first transport in the Rpc_Binding_Order Registry line. Theclient waits for a transport to time out before attempting to use the nexttransport listed. To improve connection time to a server, edit the binding orderso the client uses the first binding in the list to connect to the server. Thebinding order you use depends on the protocols your server and client support.On TCP/IP protocols, the binding order depends on the name resolutionmechanism.

You can change the Outlook client's binding order in the Exchange Registry.Go to the HKEY_LOCAL_MACHINE SOFTWAREMicrosoftExchange ExchangeProvider Rpc_Binding_Order"="ncalrpc,ncacn_ip_tcp,ncacn_spx,ncacn_np,netbios,ncacn_vns_spp Registry key. To changethe binding order on one or two machines, you can edit the Registry. If you needto make widespread changes, or you want your changes to be part of the standardinstallation, refer to the Microsoft Support Online article "XGEN: Changingthe RPC Binding Order" (http://support.microsoft.com/support/kb/articles/q163/5/76.asp).

We performed tests to determine which RPC binding order works with whichnetwork protocol. We put Outlook on an NT server, and we configured an NT serveras an Exchange server. Table 2, Table 3, and Table 4 show the results for theTCP/IP, NetBEUI, and IPX/SPX protocols, respectively. Each network protocolallowed access only through specific RPC binding orders. We reconfigured Outlookto test each network binding. The order of binding options is unimportant if youplace the preferred binding at the beginning of the list. The preferred bindingdepends on the protocol your Exchange server supports.

If your workstation uses IPX/SPX and TCP/IP but the Exchange server usesonly TCP/IP, your RPC binding order must list TCP/IP as the first binding. IfIPX/SPX is first, Outlook tries to connect via IPX/SPX, times out, and triesanother protocol. These unnecessary steps slow your connection speed. If you useNamed Pipes, Outlook tries to connect via TCP/IP or IPX/SPX, depending on yournetwork settings search order for LANA bindings.

Name Resolution
After Outlook determines the communications pathway, it must resolve theExchange server's name. Outlook's name resolution method depends on the RPCbinding. When Outlook connects to an Exchange server, it relies on the currentprotocol's name resolution method. How long the Outlook client takes to resolvethe Exchange server name depends on the protocol and resolution method it uses.Table 5 lists the available protocols and name resolution methods, in the orderin which the client uses them.

LANA uses standard name resolution over the first protocol bound to thenetwork card, as specified in the Registry by LANA 0. Table 6 lists LANAresolution methods for the specified protocols, in the order in which LANA usesthem.

Clients using NetBEUI, IPX/SPX, or Vines IP protocols employ broadcast nameresolution. TCP/IP has more difficult name resolution than the other protocols,because it uses different IP address resolution pathways.

Changing name resolution order. The binding order determinesthe connection type and the name resolution method Outlook uses, because bothmechanisms relate to a protocol. On TCP/IP networks, the name resolution methoddepends on the type of NetBIOS node you configure your client for--that is,hybrid node (h-node), mixed node (m-node), point-to-point node (p-node), orbroadcast node (b-node). You must understand when the client communicates withthe server and how to modify communication to optimize performance.

On TCP/IP networks, the default name resolution method is Domain NameSystem (DNS), which creates problems. The name resolution search begins with DNSquerying. If you have a DNS server that doesn't resolve the Exchange servername, Outlook continues querying the DNS server. Outlook repeats the DNS queryas many as 10 times before moving to another resolution mechanism, and eachquery takes more than a minute. On a TCP/IP network, use TCP/IP as your firstbinding order to eliminate the DNS querying problem.

When Outlook uses TCP/IP as the network protocol and as the first RPCbinding option, the connection is a sockets connection. Therefore, Outlook usesthe Windows Sockets (Winsock) name resolution order, as Table 7 outlines. IfNetBEUI is your network protocol, select Named Pipes for your first bindingorder. On IPX/SPX clients, select IPX/SPX as the first binding order.

We used TCP/IP as the network protocol and performed name resolution testson three NT servers (an Outlook client, an Exchange server, and a sniffer) tovalidate the name resolution order for each binding order. We expected thencacn_np binding order to use the NetBIOS name resolution search order. However,ncacn_np and ncacn_ip_tcp used the Winsock name resolution search order, asTable 7 shows. These bindings attempt to use DNS for name resolution (if youconfigure the client for DNS), so you need to make some adjustments when you setup Outlook to avoid the increased connection time we discussed earlier. You canset up a DNS server in your organization to support the Exchange server, or youcan create HOST file entries.

When we connected to the company's network through Remote Access Service(RAS) or Dial-Up Networking (DUN), the RAS configuration prevented us fromaccessing the client's DNS server. The DNS server did not respond to theclient's request and thus delayed Outlook's startup. After the DNS query timedout, the client checked the NetBIOS name cache, Windows Internet Naming Service(WINS) server, broadcast, and LMHOSTS file. To prevent this delay, we placed theExchange server's IP information in the client's HOSTS file.

Managing Message and Address Storage
For optimal performance, the Outlook client must efficiently accessinformation from the server. You can configure Outlook to access the server inseveral ways. The client software communicates with the server to send andreceive messages and to access the global address list (GAL) and public folders.You can control how often this communication takes place. Modifyingcommunications timing preserves network bandwidth.

You must decide where to store messages, addresses, and archiveinformation. You can store messages and addresses on the Exchange server(within the Exchange database) or outside the Exchange database. Addressinformation within the Exchange database forms a GAL, and address informationoutside the database forms a personal address book. You can use the contactsapplication to store information within or outside the Exchange database.Archive information includes old messages and meeting requests.You maintain this information on a workstation or file server.

Messages. You configure the client to dictate where it stores messages. You can configure Outlook to keep messages inpersonal folders (.pst files) or in offline storage (.ost) files. The Microsoft Outlook 97 Administrator's Guide (http://www.microsoft.com/outlook/adminguide) provides complete details about these files.You need to understand how each mechanism affects your networking and where to store the two file types.

You can store .pst files on your workstation or server. When you use a .pst file to store your inbox messages, Outlook funnels messages from the Exchange server to the .pst file. If you maintain the file on your workstation, messages move across the network from the server to the workstation only once. You can quickly read .pst messages because no network traffic is involved. Storing .pst files on your workstation has two disadvantages: You need to use backup strategies to prevent data loss, and you need to share your hard disk if you want to access your messages from another machine. In addition, Exchange places an exclusive lock on open .pst files, so you can't access your messages from aremote machine if your local machine uses Exchange.

If you store .pst files on a server (file share), Outlook moves messagesfrom the Exchange server to the .pst file. As Figure 1 shows, this procedurerequires two network transactions: one to move the message to the client andanother to move the message to the file server. When you try to read a messagein Outlook, a third network move occurs, to move the message back from the fileserver to the client. Deleting a message generates additional network traffic.

You maintain .ost files on your workstation. An .ost file maintains asynchronized copy of information from the server. If you have an inbox in the.ost file, incoming messages move from the server to the .ost file only once.You then work from a local message store. You specify the frequency for updatingoffline storage. If network bandwidth availability is inconsistent, you can use.ost files and synchronize events to improve performance. Offline foldersincrease the availability of messages. Outlook synchronizes the .ost file withthe server, so you can maintain backups at the server, and you can retrievemessages from any workstation with access to the Exchange server.

If you store .ost messages on a server, the messages move across thenetwork each time you access them. If you read messages only once and deletethem, you generate the same amount of network traffic as if you used a local.pst file. Deleting messages without reading them (i.e., reading only theheader) reduces network traffic. Reading messages multiple times generatesexcessive network traffic. Consider how you will access messages to determinethe best storage option.

Addresses. You can maintain address information on theserver (GAL) or the workstation or file server (personal address list). Eachtime you attempt to send a message, you access this information.

Working offline lets you use a locally cached copy of the GAL. This cachedGAL resolves names more quickly than if you access the list over a WAN link. Ifyour address book changes frequently, you must download it more often tomaintain a current file.

You can maintain a personal address book (.pab) file locally on yourworkstation or remotely on a file server. File server storage provides centralaccess if you switch machines, but it requires more network attention. Instead of using the .pab file, you can use the mailbox contacts to store personal addresses. One drawback is Outlook's inability to incorporate contact resources into distribution lists. This feature would eliminate the need for personal address books.

Archive information. Archiving messages can causecomplications. You can archive messages you stored as .pst files or messages you stored on the server. The archive file is a .pst file, so if you archive.pst-stored messages, you move messages from one .pst file to another and thus create additional network traffic. The amount of network traffic you generate depends on where you store the archive .pst files. The default archive file location is the NT or Win95 profile path. If you use server-based profiles, the archive file follows you. Outlook copies the file as part of your profile, so your logon and logoff time increases as the file gets larger.

Outlook 98
Improperly configuring the client software can cause performance problems in Outlook and Exchange. Outlook 98 includes several enhancements. For example, many communications tasks that currently tie up the workstation are background tasks in Outlook 98, giving you more time to read and compose messages. If you haven't upgraded to Outlook 98, consider doing so.