Microsoft will block online Exchange Web Services API – but gaps remain with Graph alternative

Microsoft will block online Exchange Web Services API – but gaps remain with Graph alternative

Microsoft will retire Exchange Web Services (EWS) for Exchange Online, other than for its own applications, from October 2026, despite not yet addressing gaps between this API and the recommended Graph alternative.

EWS is an XML-based API, using SOAP (Simple Object Access Protocol) that was introduced in Exchange Server 2007. Microsoft Graph is a REST (Representational State Transfer) API which supports OAuth 2.0 authentication and covers not only Exchange Online but also other services. 

Microsoft first stated that it would freeze EWS in 2018, at which time the team said that Basic Authentication access for EWS would be unsupported from Oct. 13, 2020, and that EWS “will no longer receive feature updates.”

Despite that announcement, some developers still use EWS, primarily because it allows access to services that Microsoft Graph does not, including access to public folders and archive mailboxes.

In October 2021 Microsoft again deprecated EWS for Exchange Online, stating that it would remove support for the “25 least used APIs of EWS for Exchange Online” from March 31st 2022. Microsoft also said that it would “remove the ability to create new EWS apps starting September 30, 2022,” but later backtracked “based on customer feedback.”

The frustration for developers is that while Microsoft urges them to move to Microsoft Graph, it simultaneously prevents them from doing so, by not implementing access to all the services that EWS covers. “Right now, the Exchange Web Services API is the only way to get full-fidelity (preserving all properties) email information into and out of Office 365” remarked one in response to the 2021 post.

Another said “EWS is complete. graphAPI is not when it comes to a full featured Exchange API.”

The latest post has prompted similar responses. In reference to the gaps in functionality between EWS and Graph, one comment said that “Those same gaps have been repeatedly brought by the community/ISVs since the original “deprecation” notice, yet 5 years later we’ve seen zero movement on that front. Are you actually going to address them?”

Another issue facing developers who market Exchange-based applications is that on-premises Exchange does not support the Graph API at all. On-premises Exchange will continue to support EWS; but this means that Exchange Online and Exchange on-premises have two different APIs causing extra work for solutions that support both.

Microsoft also appears to be making exceptions for its own applications. The new post states that “on October 1, 2026, we will start blocking EWS requests from non-Microsoft apps to Exchange Online … the changes in Exchange Online do not affect Outlook for Windows or Mac, Teams, or any other Microsoft product.” The choice of words – “blocking” rather than “removing” – suggests that the EWS APIs will still exist after that date but third-parties will no longer be able to use them.

Microsoft’s Luberth Morera, Senior Program Manager on Microsoft Graph, said in a comment that the team is working to address some missing features. “Yes, we are already addressing many of these. We will update this same thread when major features hit either beta or v1 endpoints,” he said.

Even if this is the case, one important feature which seems uncertain is access to public folders. “We are reviewing the need to provide third-party app access to Exchange Online public folders via the Graph API,” the post said, presumably a review that has been running at least since 2018.

Public Folders, allowing shared access to calendars, contacts and other data, were a key feature of Exchange in its early days, and many organizations became dependent on them and migrated them to Exchange Online. Microsoft has other ways to share such data, all of them with different features, and migration is not always easy.