MS Outlook Interoperability: Digging Deeper
  
By John Jacobs
AT A GLANCE:
Technical Level: Medium	Audience: Administrators, Help Desk personnel	

Article Section	What's There	

Messaging 	How earlier clients perform messaging, how Outlook does it, and why the similarities prevent most upgrade and interoperability problems. The third subsection explains how to apply the specific recommendations made in the Outlook whitepaper "Interoperability with MS Exchange, MS Mail 3.x, MS Schedule+ 95 and 1.0."	
Scheduling 	How earlier clients perform scheduling, how Outlook does it, and how the differences between these can create problems during upgrades. The third subsection explains how to apply the specific recommendations made in the Outlook whitepaper Interoperability with MS Exchange, MS Mail 3.x, MS Schedule+ 95 and 1.0.	
More Information	Titles of and URLs to information on TechNet and the Web.	
Introduction
  
The whitepaper Interoperability with MS Exchange, MS Mail 3.x, MS Schedule+ 95 and 1.0 explains how upgrading to Outlook can impact users and how administrators can plan ahead to minimize disruptions. While the whitepaper identifies common symptoms and shows administrators how to avoid the problems they indicate, it does not dwell on causes. This article supplements the whitepaper by examining the underlying causes of interoperability problems to help administrators and support staff more efficiently deploy Outlook. Outlook differs from earlier products in many ways, but only a few cause interoperability concerns. 
The first section compares Outlook with earlier messaging clients (Microsoft Exchange Client and MS Mail 3.x), and the second compares it with earlier scheduling products (Schedule+ 95 and Schedule+ 1.0). Both sections summarize how Outlook and the earlier clients work, highlighting the key similarities and differences, then present the whitepaper's deployment advice in bold type and explain the interoperability issues. The article concludes with other sources of information.
Messaging
  
Outlook stores information in nearly the same way as the Microsoft Exchange client, and this is why upgrades to Outlook are usually smooth and interoperability is seamless during phased roll-outs. 
How the Messaging Clients Work
  
MS Mail post offices are basically shared directory structures located on file servers. Clients drop off and pick up message files on these servers, but most types of clients store received messages on their local hard disks rather than leaving them on the server.
Microsoft Exchange, in contrast, is a client/server messaging system. Client code on users' computers communicates with the Microsoft Exchange Server service, running on the server computer, by sending Mail Applications Programming Interface (MAPI) messages. The server service adds messages to, and deletes them from, a message store located on the server. Clients can store messages locally, but generally leave most information on the server. The message store is highly extensible: the Microsoft Exchange Server organizes the store with predefined folders and properties, but newer clients can create new folders and new properties to support new functionality. 
Outlook, like the Microsoft Exchange client, uses MAPI to communicate with the server and in this respect is a simple upgrade of the Exchange client. Because it recognizes and uses Microsoft Exchange server profiles, folders, and properties, Outlook can read messages from, and send them to, Exchange clients. Outlook offers new features, unavailable in the Microsoft Exchange client, by creating new folders and properties in the message store. Microsoft Exchange clients that open messages containing Outlook's custom properties can't read the Outlook-specific information and simply ignore it.
For example, an Outlook client's message can contain "voting buttons" because Outlook creates a custom property that stores the information needed for this feature. Microsoft Exchange clients don't recognize this custom property, so when they receive a message with voting buttons from an Outlook client they ignore the voting button information. Recipients running Outlook see the buttons; recipients running Microsoft Exchange do not.
In many cases, new clients can simulate new functionality for older clients by storing data in old properties as well as in new ones. For example, both Outlook and Microsoft Exchange let users create and save new views, but in order to support more flexible views Outlook stores views using a different format, in a different folder property within the message store. To maintain compatibility, Outlook provides a Convert to Exchange Views option that saves tabular views created in Outlook in both Outlook and Exchange formats.
Messaging Interoperability
  
Because they use the same message store and profiles, Outlook and Exchange clients can:
·	Send each other messages, with rich text, attached objects (including attached messages), and hyperlinks
·	Use the same personal address books
·	View the same public folders, and the same table views
·	Operate without hardcoded message size limits
·	Use MS Word 97 WordMail
Most interoperability issues result from new Outlook features that the Microsoft Exchange client does not support because it does not recognize Outlook's new folders and properties:
·	Non-table views, such as Journal and Calendar (described below)
·	New format for saving views
·	Attached objects that are Outlook-specific, such as attached Contact or Task items
·	A new way to store forms, which lets Outlook forms support ActiveX controls and MS Office document templates
Some issues, however, arise because Outlook's new functionality prevents it from supporting Microsoft Exchange features: 
·	Outlook relies on MS Word 97 WordMail, and can't use MS Word 95 WordMail
·	Outlook's Inbox Assistant feature can read most rules created by the Exchange client's Inbox Assistant, but those that refer to Exchange Forms Designer (EFD) forms must be recreated
Deployment Advice Reviewed
  
Most organizations migrate in phases, so that users can receive training and IT staff can provide support without either group losing productivity. Administrators need to decide which users to migrate in each phase. The general rule is to migrate everyone in a workgroup at the same time. Here are summaries of additional advice found in the whitepaper:
Users can migrate only if they use a platform on which Outlook software is available (Windows 95 and Windows NT 4.0). Otherwise, they need to continue using the Exchange or MS Mail 3.x client.
Users should migrate early if they need Outlook's new features, most of which are implemented using custom folders and properties that Exchange doesn't recognize. These features include: 
·	Enhanced standard message form
·	Extended message properties, such as voting buttons, message flags, and so on
·	Private items
·	Non-table views
·	Outlook-specific forms capabilities
·	Voting buttons
·	Custom field types, such as formula and combination fields
·	Messages attached to other messages
Users who need to use WordMail must install MS Word 97 before upgrading to Outlook.
Scheduling
  
Earlier scheduling clients, such as Schedule+ 95 and 1.0, store data quite differently than Outlook, and the differences can lead to several interoperability issues.
How the Calendaring Clients Work
  
Schedule+ is a stand-alone application that stores one copy of calendar information on the client's local drive and one on a file server. The user works primarily with the local copy and the client software replicates changes to the server copy. Schedule+ can find other users' server-side files and, with proper permissions, open and alter them. For example, to book a meeting, a user typically opens other users' server-side files, checks the free/busy status of various time slots for each invitee, and then either directly alters the other users' file ("direct books" the meeting) or sends a meeting request message via e-mail. When these invitees accept, their own copies of Schedule+ book the meeting into their local files and replicate the changes to their server-side files. Conceptually, Schedule+ 1.0 and Schedule+ 95 both work this way, although the former uses a .CAL extension for data files, and the latter uses an .SCD extension. 
Outlook typically stores calendar information in a special folder within the main server-side message store, and also keeps some information in a folder in a local data store. The Calendar folder has its own, non-table views to display calendar information, but it is basically just another part of the message store, not in a separate file. Outlook supports the same group scheduling functionality as Schedule+, but instead of the client opening an .SCD or .CAL file on a file server, Outlook opens other Outlook users' Calendar folders.
Scheduling Interoperability
  
The main interoperability issues hinge on these facts:
·	Outlook can open and alter Schedule+ files, but Schedule+ client software cannot open Outlook Calendar folders in a MAPI data store.
·	Outlook's Calendar folder contains properties that have no equivalent in the Schedule+ files, so Outlook can import data from Schedule+ files but cannot export data back to them.
·	MS Mail does not provide a server-side message store, so Outlook clients with an MS Mail server compensate by working primarily with their local data stores, which other Outlook users cannot access.
·	Outlook users can direct-book appointments into Schedule+ accounts, but neither Outlook nor Schedule+ users can direct-book appointments into Outlook users' folders.
Deployment Advice Reviewed
  
Upgrade users in delegate relationships at the same time, regardless of their workgroups. Delegate relationships require that the members can open each others' calendar information, and this is possible only if both use the same client and the same back-end.
Upgrade all members of a workgroup at the same time.
Upgrade resource accounts, such as conference rooms, after upgrading the users who use those resources. If you upgrade resource accounts to Outlook while users are running Schedule+, those users will not be able to open the resource accounts' Calendar folders, and so will not be able to book those resources. In a typical case, users could invite each other to a meeting, but could not reserve a conference room because their Schedule+ client software couldn't direct-book the meeting in the Calendar folder for the conference room's account.
During the Outlook upgrade, choose the option to continue using Schedule+, rather than using Outlook for scheduling. Users typically migrate to Outlook in phases for messaging, and after the messaging migration is complete, everyone migrates at the same time from Schedule+ to Outlook.
Make sure users do not delete their Schedule+ files until everyone is ready to migrate to Outlook for scheduling. Outlook cannot export its calendar data back to Schedule+ files, so if users delete those files they must be retrieved from backup copies, or the data for new meetings and appointments must be reentered by hand into Schedule+.
If you use an MS Mail back-end, users in delegate relationships should not upgrade to Outlook for scheduling; instead, they should continue using Schedule+. Outlook works with MS Mail back-ends by storing both messaging and calendar information locally. However, Outlook clients cannot access other Outlook clients' local data stores. Outlook with an MS Mail back-end therefore cannot participate in delegate relationships. 
Each resource account, such as those for conference rooms, should have a delegate account, and that delegate account should be signed-on to Outlook on a continuously-running computer. Outlook does not support direct-booking, so users cannot book a resource by directly altering its Calendar folder. Instead, a user sends the resource's account a message requesting a meeting, and it (or its delegate) must be running Outlook in order to receive the message and act on it.
Conclusion
  
The numerous troubleshooting recommendations in the "Interoperability with MS Exchange, MS Mail 3.x, MS Schedule+ 95 and 1.0" whitepaper actually stem from a small set of technical differences between Outlook and earlier client software. This article has explained these differences so that administrators can more effectively apply the whitepaper's advice to their own networks. 
More Information
  
On TechNet
  
The whitepaper, Interoperability with MS Exchange, MS Mail 3.x, MS Schedule+ 95 and 1.0, is located in the Outlook Technical Notes.
The MS Office 97 Resource Kit is a great source for technical information about Office 97 components, including Outlook.
Several articles discuss MS Exchange migration.
The Schedule+ 95 bin has additional articles about interoperability.
Elsewhere
  
Microsoft's World Wide Web is the best place to find information related to Outlook, Exchange, Schedule+, and messaging and scheduling in general.

Interoperability with MS Exchange, MS Mail 3.x, MS Schedule+ 95 and 1.0	http://www.microsoft.com/outlook/documents/ot97inwp/default.htm	
General information about MS Office 97	http://www.microsoft.com/msoffice/	
Specific information about MS Outlook	http://www.microsoft.com/outlook/	
Information about MS Exchange	http://www.microsoft.com/exchange/	
Information about MS Schedule_ 95	http://www.microsoft.com/msscheduleplus/	
Microsoft TechNet
February 1997
Volume 5, Issue 2