API Deprecations Signal the Demise of Exchange Web Services

EWS Sunset Will Impact Office 365 Tenants and ISVs

Microsoft’s October 5 announcement that they will decommission 25 Exchange Web Services (EWS) APIs by March 31, 2022, contains some clear signals that EWS is on a short runway to oblivion. Microsoft says that the set of 25 APIs selected to go first (Figure 1) are those least used with Exchange Online.

Exchange Web Services APIs due for deprecation by March 31, 2022
Figure 1: Exchange Web Services APIs due for deprecation by March 31, 2022

Microsoft also says that they’ll remove the ability to create new EWS apps starting on September 30, 2022. Both steps are part of the sunset process to ease EWS out of Microsoft 365, with Microsoft noting that “EWS is a legacy API surface that has served us well, but no longer meets the security and manageability needs of modern app development.”

Figuring Out the Impact

Microsoft created EWS as a SOAP-based protocol to allow ISVs access to Exchange Server content. In fact, when it appeared in Exchange 2007, EWS was the first successful API for Exchange that Microsoft delivered since MAPI. Since then, EWS has been used by Microsoft in the Entourage and Outlook for Mac clients and by ISVs for many different purposes, including migration of mailbox and PST data to Exchange Online and as the foundation for backup products.

The introduction of the Microsoft Graph APIs as the preferred access method for data across Microsoft 365 marked the beginning of the end for EWS. The first sign was Microsoft’s July 2018 announcement that EWS would receive no further feature updates. In many cases, a static API is a dead API, especially when its owner’s attention is directed firmly at another API.

It’s hard to deny that Microsoft is wrong to force people towards the Microsoft Graph APIs at this point. The Graph APIs are newer, used across Microsoft 365, support standards like OAuth and OData, and its REST-based model is familiar to many programmers. The wide range of tools like the Graph Explorer and SDKs in different programming languages make it easier for developers. It’s also true that the Graph APIs have more granular security policies. But the biggest thing is that the Graph is where the puck is going.

The second sign was the inclusion of EWS in the set of connectivity protocols which Microsoft plans to disable for basic authentication. The latest turn-off date is October 1, 2022.

All of which brings us to the need for organizations to figure out how EWS is used inside their tenants and draw up plans for its replacement. The focus areas to look for EWS include:

  • Custom home-built programs and PowerShell scripts.
  • Third-party clients and client add-ons.
  • Third-party products.

Every organization is different and EWS has been around for a long time. The two factors make it difficult to give a definitive set of guidelines for what to look. Three obvious areas are migration, connectors, and backup. Any product which streams information into or out of Exchange Online should be questioned to establish what API is in use. Most backup products for Exchange Online use EWS. The protocol was never intended as the foundation for backup, but nothing else is available so ISVs have used what they can.

Searching for a Graph Replacement

As they digest the news that EWS is in terminal decline, ISVs will naturally look for a replacement. Right now, the Microsoft Graph APIs cover Outlook (mail) and other objects stored inside mailboxes like tasks, notes, and contacts. However, there isn’t any obvious Graph API to handle large-scale streaming of mailbox content of the type usually experienced in backup and restore operations.

Microsoft has just released a Graph export API for Teams which is deemed suitable for backup and restore scenarios. However, that API comes with consumption meters and a per-message charging model which creates a whole new economic model for pricing for backup data. The volume of Teams messages is lower than Exchange Online email and the size of Exchange Online mailboxes is larger (even with the new 1.5 TB limit for auto-expanding archives). If Microsoft decides to impose the same consumption pricing model on an export/import API for Exchange Online, it could create many headaches for customers and ISVs alike to deal with the costs associated with scenarios like:

  • Moving data from legacy archive solutions to Exchange Online.
  • Importing data from third-party systems into Exchange Online (connectors).
  • Tenant-to-tenant migrations of Exchange mailboxes and archives.
  • Backup processing for Exchange Online mailboxes (user, shared, group, public folder, and other) to external third-party datacenters.

Although all the signs are that EWS will slip away soon, Microsoft hasn’t set a final (public) date for the removal of EWS from Exchange Online. You could put your head into the sand and hope that the protests of customers and ISVs will be sufficient to force Microsoft to keep EWS going for longer. I don’t think that’s a great strategy. It’s better to accept that the days of EWS are numbered (in the low hundreds) and start working on replacement components for your IT infrastructure. You know it makes sense.


Learn about Exchange Online and the rest of the Office 365 ecosystem by subscribing to the Office 365 for IT Pros eBook. Use our experience to understand what’s importance and how changes affect your tenant.

Leave a Reply

This site uses Akismet to reduce spam. Learn how your comment data is processed.