Customization, Add-ins, and Resources for Exchange Online

Office 365

Applies to: Office 365

Topic Last Modified: 2018-06-13

Administrators can connect many kinds of on-premises and hosted applications to Exchange Online, including custom line-of-business applications and software from third-party vendors.

The application vendor must provide support for the application and perform all related application compatibility testing.
Custom applications cannot be hosted in a Microsoft data center, unless they are hosted on the Microsoft Azure platform.
Exchange Online does not host custom code or third-party applications, including DLLs and custom code packaged in transport agents, or allow modifications to files on servers in the data center.
Applications that send email messages are subject to the same recipient limits and message rate limits as regular Exchange Online mailboxes.

Exchange Online supports the following application development tools, application programming interfaces (APIs), and native tools:

  • Outlook Add-Ins and Outlook MAPI   Most Outlook add-ins will work with Exchange Online. Most custom applications that use the Outlook MAPI library can connect to Exchange Online. If a custom application requires Outlook to be installed in order to function, it probably uses the Outlook MAPI library.

    Microsoft does not provide support or troubleshooting help for Outlook add-ins. Customers must contact the vendor that created the add-in for assistance.
  • Reporting Features and Troubleshooting Tools   Includes various reporting features including the message trace and delivery reports features. For more information, see Reporting Features and Troubleshooting Tools.

The following APIs are unavailable for use with Exchange Online:

  • Exchange Server MAPI/CDO   Some third-party applications use Exchange Server MAPI Client and Collaboration Data Objects (MAPI/CDO) for server-to-server communication with Exchange. These applications need to be installed within the same local network as Exchange and will not connect over the Internet to Exchange Online.

  • WebDAV   The Exchange WebDAV API was removed from Exchange Server 2010 and is not available in Exchange Online.

Documentation, resources, and end-user training are the keys to successful Office 365 and Exchange Online adoption. Microsoft provides a range of administrator and end-user documentation and tools online to help customers develop a program for effective adoption of Office 365 and Exchange Online. Microsoft partners can provide additional deployment, administration, and end-user training by customer request.

Exchange Online Resources

End-User Resources

Deployment and Developer Resources

To view feature availability across Office 365 plans, standalone options, and on-premise solutions, see Exchange Online Service Description.