Overview of Outlook 2013 planning
Applies to: Outlook 2013, Office 365 ProPlus
Topic Last Modified: 2013-12-18
Summary: Learn about what you should consider when you deploy Outlook 2013.
A close review of the organization's messaging requirements will help you plan the optimal Outlook 2013 deployment.
In this article:
The organization's messaging environment helps shape the Outlook 2013 deployment. Factors to consider include whether you are upgrading Outlook, installing the application for the first time, planning for roaming or remote users, or choosing a combination of these and other factors.
The new Office is available in two delivery formats: Windows Installer-based (MSI) and Click-to-Run. Traditional Windows Installer-based deployments of Office 2013 are available for enterprise organizations through volume licensing. Office 2013 Click-to-Run is available with an Office subscription of Office 365 ProPlus. Users who do not have Office 365 accounts can download Office 2013 from Office.com.
The Office 365 ProPlus offering provides the complete Office client suite as a monthly subscription service. Office 365 ProPlus is part of the Office 365 product suite and is downloaded and managed through the Office 365 portal. The download process for Office 365 ProPlus is known as Click-to-Run, a streaming and virtualization technology that is designed to significantly reduce the time that is required to download and use Office 365 ProPlus client products. Streaming enables users to begin to use a Click-to-Run program before the complete program is downloaded. For more information, see Overview of Office 365 ProPlus.
Administrators who have signed up for Office 365 can also stage and deploy Click-to-Run products from an on-premises location. This is useful in scenarios where administrators want to minimize the demand on the network or to prevent users from installing products from the Internet because of corporate security requirements. To stage a deployment on-premises, administrators use the Office Deployment Tool for Click-to-Run. For more information, see Office Deployment Tool for Click-to-Run.
The MSI and Click-to-Run versions of the new Office and Outlook 2013 have different configuration options and administration tools. For the Click-to-Run version of Outlook 2013, you can change the settings from the default configuration by deploying Group Policy settings or registry keys. For the MSI version of Outlook 2013, you can use Group Policy and the Office Customization Tool (OCT) to specify user settings. If you want to enforce specific settings, you must use Group Policy. For more information, see Office Customization Tool (OCT) reference for Office 2013 and Overview of Click-to-Run customization.
If you are upgrading to Outlook 2013 from an earlier version of Outlook, consider whether you will migrate previous settings, change user profiles, and use new customization options. By default, user settings are migrated automatically, except for security settings. Customization of Outlook settings is optional and only needed if you want to change the settings from the default configuration. Also Outlook can automatically create a new Outlook profile by using the Account Auto Configuration process (Autodiscover). If you are deploying Office 2013 (a MSI deployment), the Office Customization Tool (OCT) enables you to migrate users' current settings and make other customizations. For example, you can define new Microsoft Exchange servers or customize new features. If you are deploying Office 365 ProPlus and must change settings from the default configuration, you can use Group Policy or the registry.
If you are deploying Outlook on client computers for the first time, you should use the Account Auto Configuration process (Autodiscover) to automatically create new Outlook profiles. If you are deploying Office 2013 and must change settings from the default configurations, you can use the OCT to define profile settings for users. If you are deploying Outlook as part of Office 365 ProPlus, you can deploy registry settings to define profile settings.
For more information, see the following articles.
When you upgrade from Office Outlook 2003, Outlook 2007, or Outlook 2010 to Outlook 2013 Outlook data is migrated. Data migration from versions of Outlook earlier than Office Outlook 2003 and other email applications is not supported in Outlook 2013.
You can customize Outlook to optimize the experience for remote and roaming users, and to set up Outlook for multiple users on the same computer.
You might want to configure features such as Outlook Anywhere (known as RPC over HTTP in earlier versions of Outlook) and Cached Exchange Mode for remote users. These features enhance the user experience when Outlook is used over slower or less reliable connections. By using Outlook Anywhere, you can configure connections that enable users to connect more securely from the Internet to Exchange servers in your organization or to Exchange Online without using a virtual private network (VPN) connection. Cached Exchange Mode is an Outlook feature that was introduced with Office Outlook 2003. It creates a local copy of users' mailboxes. Cached Exchange Mode is recommended for all configurations, but especially benefits remote users. The feature enables users to have more reliable access to their Outlook data, whether or not they are connected to a network. For more information, see Configure Outlook Anywhere in Outlook 2013 and Plan a Cached Exchange Mode deployment in Outlook 2013.
When multiple users share the same computer, use Windows logon features on the computer's operating system to manage user logon verification. Unless you deploy the Click-2-Run version of Outlook which is available with Office 365 ProPlus, users must use the same version of Outlook. If you deploy the Windows Installer-based (MSI) version of Outlook, only one version of Outlook can be installed on the same computer. See Supported scenarios for more information. To learn more about how to set up multiple Outlook users on the same computer, see Using Outlook on a computer you share with other people .
Office 2013 provides broad support for deployment in international or multilingual environments. As with the 2007 Microsoft Office system and Office 2010 suites, the Office 2013 product consists of the language-neutral core package plus one or more language-specific packages. In addition to the proofing tools that are included in each language version, you can download and deploy proofing tools for other languages to help multilingual groups work with and edit files in many languages. For more information, see Plan for multilanguage deployment of Office 2013.
Outlook 2013 supports Unicode throughout the product to help multilingual organizations seamlessly exchange messages and other information in a multilingual environment.
Some features of Outlook 2013 (for example, Cached Exchange Mode) require Exchange Server as a messaging platform. Although Outlook 2013 works well with earlier versions of Exchange, some features of Outlook 2013 require specific versions of Exchange. Because of this and other improved integration with Exchange throughout Outlook 2013, we recommend that you combine Outlook 2013 with the latest version of Exchange Server or use Exchange Online. For more information, see Outlook 2013 features supported by different versions of Exchange Server.
Deployment customization decisions for Outlook 2013 depend on which version of Exchange Server you use. If you currently use Exchange Server as your messaging server and you have not upgraded to Exchange 2007 or a later version, consider coordinating the Exchange Server upgrade or Exchange Online migration with the deployment timing for Outlook 2013. Exchange Server 2007 is the earliest version of Exchange Server that can be used with Outlook 2013.
If you have an on-premises Exchange Server and plan to add Exchange Online to co-exist in your environment, there are two things to consider:
There is no cross-premises manager delegation. If the manager’s account is connected to Exchange Online, the delegate’s account must be on Exchange Online too.
An account that is on-premises cannot have “Send As” permissions for an account that is connected to Exchange Online.
Also be aware that the user authentication method is different between an on-premises Exchange Server and Exchange Online. An Exchange Online user enters his or her email address (as the user name) and password. However, the user can decide to save the password so that the user only has to enter it one time.
You have options for when and how you install Outlook 2013. For example, consider whether which of the following would be best for your organization:
Install or upgrade Outlook for different groups of users in stages, or at the same time.
Install Outlook as a stand-alone application.
Install Outlook before, during, or after an Office 2013 installation.
Each organization has a different environment and might make a different choice about timing Outlook 2013 upgrades. For example, you might have a messaging group that is responsible for upgrading Outlook and a separate group that plans deployment for other Office applications. In this case, it might be easier to upgrade Outlook separately from the rest of Office, instead of trying to coordinate deployment between the two groups.
Note that the MSI version of Outlook 2013 cannot coexist with earlier versions of Outlook on the same computer. However, you can install a Click-to-Run version of Outlook 2013 to run side-by-side with Outlook 2007 or Outlook 2010. However, side-by-side installations of Outlook 2013 with earlier versions of Outlook, such as Office Outlook 2003 are not supported.
You can customize an MSI installation of Outlook to handle Outlook user settings and profiles in two ways:
Specify Outlook user settings in the OCT.
Specify options for managing new and existing Outlook profiles in the OCT or use an Outlook Profile file (.prf).
For example, you can enable Outlook users to migrate their current profiles and settings while default profiles and settings are defined for new Outlook users. You can also change existing profiles and establish new default profiles for new Outlook users. If you deploy Outlook 2013 together with Exchange Server 2010 or Exchange Online, you can add more than one Exchange account for a profile by using the OCT or .prf file.
When you use the OCT to customize Outlook, you save choices and other installation preferences in the customization .msp file that is applied during Setup. Later, you update settings and profile information by opening the file in the OCT and saving a new copy of the file.
For more information about how to configure Outlook profiles, see Office Customization Tool (OCT) reference for Office 2013 and Customize Outlook profiles by using an Outlook Profile (PRF) file. These articles also apply to environments that have Exchange Online deployed.
For Click-to-Run installations of Outlook 2013, you can use Group Policy or registry keys to customize Outlook settings and profiles.
As with Office Outlook 2007 and Outlook 2010, Outlook 2013 includes features that let you easily subscribe to new sources of content and share the features with users inside and outside your organization. Content sources include SharePoint Foundation 2013 and SharePoint Foundation 2013 contacts, tasks, and calendars, together with local and Internet-based calendars (iCals).
Really Simple Syndication (RSS) is another sharing feature that enables users to subscribe to internal or Internet-based sources of syndicated content (.xml files) to avoid having to check a site for new information. You can deploy specific RSS feeds or calendar subscriptions to users, configure settings to manage how users can share these subscriptions or content, specify how often the servers update users' copies of the data, and more.
Remote Desktop Services in Windows Server enables you to install a single volume licensed copy of an MSI version of Outlook 2013 on a Remote Desktop Services-enabled computer. Instead of running Outlook on local computers, multiple users connect to the server and run Outlook from that server.
To achieve optimal results when you use Outlook with Remote Desktop Services, think about how you customize your Outlook configuration. For example, in Outlook 2013 you can configure Cached Exchange Mode with Remote Desktop Services. However, you will have to provide sufficient disk space to accommodate each user’s mailbox on the Remote Desktop Session Host server (terminal server). Note that Outlook might be part of an environment that includes other applications that are provided on the same Remote Desktop Session Host computer. For more information, see Cached Exchange Mode in a Remote Desktop Session Host environment: planning considerations (Outlook 2010) (white paper). Although this article is for Outlook 2010, the content still applies to Outlook 2013.
A mail app for Outlook is a cloud-enabled application that integrates rich, scenario-focused content and services together with Outlook 2013. You can obtain apps for Outlook from the Office Store. Exchange Administrators can make specific apps for Outlook available to their end-users if their Exchange accounts are on Exchange Server 2013. For more information, see Overview of apps for Office 2013.
Outlook mailboxes grow as users create and receive items. To keep mailboxes manageable, users need another place to store or archive older items that are important but rarely used. It is typically most convenient to automatically move these older items to the archive folder and to discard items whose content has expired and is no longer valid. Outlook 2013 AutoArchive can manage this process automatically for users. However, we recommend that you use the Personal Archive feature in Exchange Server 2013 Messaging Records Management (MRM) (or in Exchange Online) because it eliminates the need for Personal Folder files (.pst). By using Personal Archive in Exchange Server 2013 or in Exchange Online, the email archive folders are stored online so that users can access the archived files by using Outlook Web App or from a secondary computer by using Outlook 2013. By using either of these client applications, users can view an archive mailbox and move or copy messages between their primary mailboxes and the archive.
Note that when Personal Archive is enabled, AutoArchive is not available to the user and does not archive messages.
If you plan to deploy Outlook 2013 together with Exchange Server 2010, Exchange Server 2013 or Exchange Online, consider using the Exchange Server Personal Archive feature instead of Outlook 2013 AutoArchive. For more information, see Understanding Personal Archive: Exchange 2010 Help, Plan for compliance and archiving in Outlook 2010, and Microsoft Exchange Online Archiving.
If you choose to use the AutoArchive feature in Outlook 2013, you can configure the settings to customize Outlook 2013 AutoArchive by using the Outlook Group Policy template (Outlk15.adm). Or if you are deploying the MSI version of Outlook you can configure default settings by using the Office Customization Tool (OCT), in which case users can change the settings.
If you plan to deploy Outlook 2013 together with Exchange Server 2013 or Exchange Online, we recommend that you use the Personal Archive feature in Exchange Server 2013 Messaging Records Management (MRM) (or in Exchange Online) because it eliminates the need for Outlook data files (.pst). By using the Personal Archive in Exchange Server 2013 or in Exchange Online, the email archive is stored online so that users can access the archived files by using Outlook Web App or from a secondary computer by using Outlook 2013. By using either of these client applications, users can view an archive mailbox and move or copy messages between their primary mailboxes and the archive. For more information, see Understanding Personal Archive: Exchange 2010 Help, Plan for compliance and archiving in Outlook 2010, and Microsoft Exchange Online Archiving.
If you plan to deploy Outlook 2013 together with Exchange Server 2007, you can configure .pst files to be stored locally (recommended) or on a network share. Storing .pst files on a network share is unsupported in most scenarios. Consider storing .pst files on a network share only if the network has high bandwidth and reliability. If a user’s .pst file is stored on a network share and the user loses the connection to the network, the user might lose unsaved changes and have a poor Outlook experience.
Retention policy settings can help users follow retention policy guidelines that your organization establishes for document retention. You cannot deploy AutoArchive-based retention settings through Outlook 2013 by using Group Policy. If you must deploy retention policies, explore the Messaging Records Management (MRM) features in Exchange Server. For more information, see Messaging Records Management: Exchange 2010 Help and Plan for compliance and archiving in Outlook 2010.
Outlook includes many security and privacy features, some of which are highlighted in the following sections. For more information about how to plan for security and privacy in Outlook 2013, see Overview of security and protection settings for Outlook 2013.
Outlook 2013 includes features to help minimize the spread of viruses and to help users avoid junk email, but there are some things to keep in mind when scanning for viruses and junk email or spam.
As in Outlook 2007 and Outlook 2010, in Outlook 2013 you can configure virus-prevention and other security settings by using Group Policy to support the needs of an organization. You can also use the Outlook Security Template to configure settings, as in earlier releases of Outlook. By using either configuration method, you can, for example, modify the list of file types that are blocked in email messages.
The Object Model (OM) Guard that helps prevent viruses from using the Outlook Address Book (OAB) to spread is updated. Outlook checks for up-to-date antivirus software to help determine when to display OAB access warnings and other Outlook security warnings.
Some Outlook 2013 antivirus planning considerations
When you plan antivirus scanning for Microsoft Outlook 2013 files and email messages, take precautions to prevent the issues that can arise.
Scanning Outlook files—Outlook Data Files (*.pst) and Offline Folder files (*.ost) are the most frequently-accessed Outlook files. If you use antivirus software to perform file-level scanning on them, while Outlook is in use, data corruption issues might occur.
Data corruption issues might also occur if you scan Outlook address book files (*.oab ), Send/receive settings files (*.srs ), *.xml files, and Outlprnt, although the possibility is smaller because people access these files less frequently.
Scanning email messages—We do not recommend that you scan *.pst, *.ost, and other Outlook files directly. Instead, we recommend that you scan email message attachments on the email server and on the Outlook client computer.
To scan email messages that are on an email server, you must use antivirus software that was developed to scan incoming and outgoing e-mail.
To scan email messages that are on the Exchange Server, use an antivirus software program that is Exchange-aware.
If your email messages are on an email server that is located at an Internet service provider (ISP), verify that the ISP is using antivirus software to scan incoming and outgoing email messages.
To scan the attachments that are included in email messages on the client computer, use antivirus software on the client computer. We recommend this in case an unwanted message reaches your email client because antivirus software on the email server failed to identify it.
Outlook 2013 has several features to help users reduce receipt of junk email messages. Outlook 2013 includes a Junk Email Filter that replaces the rules that were used in earlier versions of Outlook to filter mail. Messages caught by the filter are moved to the Junk Email folder, where they can be viewed or deleted later.
Junk email senders can include a web beacon in HTML email messages that includes external content, such as graphic images. When users open or view the email, the web beacons verify that their email addresses are valid. This increases the probability that users will receive more junk email messages. Outlook 2013 reduces the probability that users will become targets for future junk email by blocking automatic picture downloads from external servers by default.
Outlook 2013 helps protect against issues that are created by phishing email messages and deceptive domain names. By default, Outlook screens phishing email messages. These messages seem to be legitimate but they capture personal information, such as a user's bank account number and password. Outlook also helps prevent the receipt of email messages from deceptive users by warning about suspicious domain names in email addresses. Outlook 2013 supports internationalized domain names (IDNs) in email addresses. IDNs allow people to register and use domain names in their native languages instead of online English. IDN support allows phishers to send homograph attacks, a situation in which a look-alike domain name is created by using alphabet characters from different languages, not just English, with the intention of deceiving users into thinking that they are visiting a legitimate website.
For more information, see Overview of security and protection settings for Outlook 2013 and Plan for limiting junk e-mail in Outlook 2013.
Outlook provides cryptographic features for sending and receiving security-enhanced email messages over the Internet or local intranet. You can customize features in an Outlook 2013 deployment to set cryptographic options that are appropriate for your organization.
You can also implement additional features to help improve security in email messaging. For example, you can provide security labels that match your organization's security policy. An Internal Use Only label might be implemented as a security label to apply to email messages that should not be sent or forwarded outside your company.
For more information, see Plan for email messaging cryptography in Outlook 2013.
Information Rights Management (IRM) helps users prevent sensitive email messages and other Office content, such as documents and worksheets, from being forwarded, edited, or copied by unauthorized people. In Outlook 2013, users can use IRM to mark email messages with "Do not forward," which automatically restricts permission for recipients to forward, print, or copy the message. In addition, you can define customized Office-wide IRM permission policies for your organization's needs and can deploy the new permission policies for users to use with email messages or other Office documents. For more information, see Plan Information Rights Management in Office 2013.
Outlook 2013 can be used with many email servers and services. The primary email servers and services supported by Outlook include the following:
Simple Mail Transfer Protocol (SMTP)
Post Office Protocol version 3 (POP3)
Internet Mail Access Protocol version 4 (IMAP4)
MAPI for Exchange Server (version 2007 and later versions)
Exchange Active Sync for connection to services such as Outlook.com (Hotmail) to access mail, calendar, contacts and tasks
Other messaging and information sources, such as Hewlett-Packard OpenMail. Use of these additional service providers is made possible by how Outlook 2013 uses the MAPI extensibility interface.
Users can use the Contacts, Tasks, and Calendar features in Outlook 2013 without being connected to an email server.
You can install Outlook 2013 over any previous installation of Outlook. As in other Office 2013 applications, user settings that are stored in the registry are migrated when you upgrade from Office Outlook 2003 or later versions to Outlook 2013. If a MAPI profile already exists on a user's computer, you typically can configure a deployment to continue to use the profile
The MSI version of Outlook 2013 cannot coexist with earlier versions of Outlook on the same computer. However, you can install a Click-to-Run version of Outlook 2013 to run side-by-side with Outlook 2007 or Outlook 2010. But, side-by-side installations of Outlook together with earlier versions, such as Office Outlook 2003 are not supported. If you determine that users have to run Outlook 2007 or Outlook 2010 side-by-side with Outlook 2013, deploy the Click-to-Run version of Outlook 2013 or deploy Outlook 2013 with application virtualization.
When you upgrade users from an earlier version of Outlook, you must make choices about how to configure user profiles, consider Cached Exchange Mode issues, and be aware of fax and forms changes.
The process of upgrading users who currently have Cached Exchange Mode enabled in Office Outlook 2003, Office Outlook 2007 or Outlook 2010 is straightforward. If you do not change Cached Exchange Mode settings, the same settings are kept for Outlook 2013.
By default, when Outlook 2013 is installed, a new compressed version of the Outlook data file (.ost) is created. This new compressed version of the .ost is up to 40% smaller than the size of the .ost files that were created in earlier versions of Outlook. If you must keep Outlook 2013 from creating a new compressed Outlook data file (.ost), use the Outlook Group Policy template (Outlk15.admx) to enable the Do not create new OST file on upgrade policy. You can find this setting under User Configuration\Administrative Templates\Microsoft Outlook 2013\Account Settings\Exchange.
Two new features are available with Cached Exchange Mode in Outlook 2013: Exchange Fast Access and Sync Slider. Exchange Fast Access combines the instant-access of Online Mode with the offline capabilities and syncing robustness of Cached Exchange Mode. This is specifically useful when synchronizing data locally would take enough time to be noticed by the user (for example, during initial synchronization, or resuming after returning from vacation). When you first start Outlook 2013, you will immediately see your most recent email messages and a completely up-to-date calendar. Outlook 2013 caches items in the background without affecting the user's experience.
Sync Slider allows an Outlook 2013 user to limit the email messages that are synchronized locally in an Outlook data file (.ost). By default, if Cached Exchange Mode is enabled, Outlook 2013 will only cache email messages from the last 12 months and remove anything older than 12 months from the local cache. Users can view messages that were removed from the local cache by scrolling to the end of an email list in a folder and clicking the message Click here to view more on Microsoft Exchange. Users can also change how many email messages are kept offline. You, as the IT Administrator, can change the default age or enforce the age of email messages that are removed from the local cache by using Group Policy or the Office Customization Tool to set Cached Exchange Mode Sync Settings. For more information, see Configuring Cached Exchange Mode.
For additional Cached Exchange Mode planning considerations, see Plan a Cached Exchange Mode deployment in Outlook 2013.
To prepare for an upgrade, you must determine answers to the following additional questions:
Should you upgrade to Exchange Server 2010 or migrate to Exchange Online to take advantage of features such as Data Loss Protection, integrated email archive, centralized rights management, support for multiple Exchange accounts, MailTips, Policy Tips, Voice Mail Preview and Protected Voice Mail? For more information, see Microsoft Exchange on TechNet, and Outlook 2013 features supported by different versions of Exchange Server.
Should you change Outlook user profiles as part of an upgrade? For example, you might define a new Exchange Server (like Exchange Online) or enable new features of Outlook 2013. For more information about how to customize Outlook profiles for the MSI version of Outlook 2013, see Office Customization Tool (OCT) reference for Office 2013 and Plan feature customizations in Outlook 2013. These articles apply to Outlook 2013 with Exchange Server 2007 and Exchange Server 2010.
How should you create and store a backup of your existing installation? Before you upgrade to any new release, we recommend that you back up existing data. For more information about how to back up Outlook files, see Back up Outlook data with the Microsoft Outlook Personal Folders Backup tool.
How will users learn about the new interface and features of Office 2013? For more information, see User readiness for Office 2013.
Will any discontinued features or new or changed functionality affect when and how you upgrade? For a list of changes from earlier versions of Outlook, see Changes in Office 2013.
Will you have to assess and remediate Outlook add-ins in your environment?
Outlook 2013 enforces a fast shutdown process for add-ins. The shutdown process prevents add-ins from causing long delays by holding on to resources after the user exits Outlook. Although this change could adversely affect some existing add-ins, add-in vendors and IT administrators can resolve those effects by forcing Outlook to revert to the standard add-in shutdown process. For more information about the new shutdown process, see Shutdown Changes for Outlook 2010. For more information about add-in assessment and remediation, see Compatibility in Office 2013.
Exchange Client Extensions (ECEs) do not load in Outlook 2013. Some third-party applications such as archiving or security solutions use ECEs and must be updated for Outlook 2013. For more information, see Announcing the deprecation of Exchange Client Extensions.
If you are installing 64-bit Outlook 2013, you must update 32-bit MAPI applications, add-ins, and macros for Outlook to 64-bit. For more information, see the next section, Considerations for 32-bit Outlook applications when upgrading to a 64-bit platform.
If you developed 32-bit Messaging Application Programming Interface (MAPI) applications, add-ins, or macros for Outlook, there are actions that you should take to change and rebuild the 32-bit applications to run on a 64-bit platform.
Starting with Office 2010, Outlook is available as a 32-bit application and a 64-bit application. Which version of Outlook you choose depends on the edition of the Windows operating system (32-bit or 64-bit) and the edition of Office 2013 (32- or 64-bit) that is installed on the computer, if Office is already installed on that computer.
Factors that determine the feasibility of installing a 32-bit or a 64-bit version of Outlook include the following:
You can install 32-bit Office 2013 and 32-bit Outlook 2013 on a supported 32-bit or 64-bit version of the Windows operating system. You can install the 64-bit version of Office 2013 and 64-bit Outlook 2013 only on a supported 64-bit Windows operating system.
The default installation of Office 2013 on a 64-bit version of the Windows operating system is 32-bit Office 2013.
The installed version of Outlook is always the same as the version of Office 2013, if Office is installed on the same computer. That is, a 32-bit version of Outlook 2013 cannot be installed on the same computer on which 64-bit versions of other Office 2013 applications are already installed, such as 64-bit Word 2013 or 64-bit Excel 2013. Similarly, a 64-bit version of Outlook 2013 cannot be installed on the same computer on which 32-bit versions of other Office applications are already installed.
MAPI applications include stand-alone applications such as Lync, Microsoft Office Communicator, and MFCMAPI, and service providers such as address book, store, and transport providers. For MAPI method and function calls to work in a MAPI application (except for one Simple MAPI function, MAPISendMail), the bitness of the MAPI application must be the same as the bitness of the MAPI subsystem on the computer on which the application is targeted to run. The bitness of the MAPI subsystem, in turn, is determined by and is always the same as the bitness of the installed version of Outlook. For information about how to prepare Outlook applications for 32-bit and 64-bit platforms, see the Outlook 2013 MAPI Reference in Microsoft Office Development in the MSDN Library, Building MAPI Applications on 32-Bit and 64-Bit Platforms, and Developing Outlook 2010 Solutions for 32-Bit and 64-Bit Systems.