Microsoft is preparing to retire Exchange Web Services (EWS) in Exchange Online, and businesses that still rely on applications using the technology need to start checking their systems.
The change does not mean that Microsoft is switching off Exchange Online, Outlook or Microsoft 365 email.
Instead, it affects Exchange Web Services, an older method that software applications can use to communicate with Exchange Online mailboxes, calendars, contacts and other Microsoft 365 data.
Microsoft has confirmed that it will begin disabling EWS for Exchange Online in October 2026, ahead of its final retirement in April 2027.
For many businesses, nothing will visibly change.
However, organisations using older software, bespoke applications or third-party integrations could discover that something behind the scenes still depends on EWS.
That makes this a change worth investigating before October rather than after something stops working.
What is Exchange Web Services (EWS)?
Exchange Web Services is an application programming interface — usually referred to as an API — that allows applications to communicate with Microsoft Exchange.
It has been around for many years and has been used by software developers to connect applications to Exchange mailboxes.
For example, an application might use EWS to:
- access a mailbox;
- read or create calendar appointments;
- work with contacts;
- retrieve messages;
- send or process email; or
- synchronise information between Exchange and another business system.
The important distinction is that EWS isn't your mailbox itself.
A business could therefore be using Microsoft 365 perfectly normally while an application operating in the background is using EWS without the end user ever knowing.
Why is Microsoft switching EWS off?
Microsoft has been moving developers away from Exchange Web Services for several years.
Its preferred replacement is Microsoft Graph, Microsoft's modern API platform for accessing Microsoft 365 services and data.
Microsoft stopped introducing new EWS functionality some time ago and has encouraged developers to migrate applications to Microsoft Graph.
The retirement is therefore not a sudden decision, but October 2026 represents an important stage in Microsoft's enforcement of that retirement.
Ultimately, Microsoft plans to remove EWS access to Exchange Online completely.
When is Microsoft EWS being switched off?
There are two dates businesses and IT administrators should understand.
1 October 2026
Microsoft plans to begin blocking EWS traffic in Exchange Online from 1 October 2026 as part of the retirement process.
This is the immediate date organisations should be preparing for.
1 April 2027
Microsoft has stated that EWS will be fully disabled in Exchange Online on 1 April 2027.
At that point, applications still dependent on EWS will no longer be able to use it to communicate with Exchange Online.
Businesses should therefore treat 2026 as the migration period, rather than waiting until the final 2027 deadline.
Does this mean Outlook or Microsoft 365 email will stop working?
No.
This is probably the most important point for ordinary Microsoft 365 users.
Microsoft is not shutting down Exchange Online, and your Microsoft 365 mailbox isn't being removed because EWS is being retired.
For most businesses using supported Microsoft applications in a conventional Microsoft 365 environment, the EWS retirement may happen without employees noticing anything at all.
The risk is primarily associated with applications and integrations that still specifically use EWS.
If your organisation uses Microsoft 365 but is unsure whether its environment, licensing or security is being managed correctly, you can learn more about KES Microsoft 365 and business IT services.
Could my business be using EWS without knowing?
Potentially, yes.
EWS is a technical component, so it isn't something most employees would ever deliberately choose to use.
Instead, it may be built into another application.
That could include older or specialist software that integrates with Exchange Online for email, calendar or mailbox functionality.
The question businesses should therefore be asking isn't:
“Do our employees use EWS?”
It is:
“Do any of the applications connected to our Microsoft 365 environment still rely on EWS?”
What types of systems should businesses check?
Every environment is different, but particular attention should be given to older, bespoke or specialist applications that interact with Exchange Online.
Examples could include:
- CRM systems;
- document-management systems;
- booking and scheduling applications;
- workflow systems;
- archiving products;
- email-processing applications;
- bespoke business software;
- calendar integrations;
- applications that monitor shared mailboxes; and
- older third-party Microsoft 365 integrations.
The presence of one of these systems does not automatically mean it uses EWS.
Modern versions may already use Microsoft Graph or another supported authentication and integration method.
However, businesses running software that has been in place for many years should make sure somebody is checking.
What about printers and scanners?
This is an area where terminology can easily cause unnecessary concern.
A multifunction printer that simply uses Microsoft 365 to scan documents to email is not automatically using Exchange Web Services.
Many devices use SMTP or another method to send email.
However, more sophisticated document-management or workflow systems associated with scanners and multifunction devices could potentially interact with Exchange in other ways.
The correct approach is therefore not to assume every scanner will stop working.
Instead, identify which systems actually communicate with Exchange Online and how they do it.
What is replacing EWS?
For developers building applications that need to interact with Microsoft 365, Microsoft's strategic replacement for much of the functionality previously provided by EWS is Microsoft Graph.
Microsoft Graph provides a modern interface for accessing Microsoft 365 services including Outlook, calendars, users, files, Teams and other Microsoft cloud services.
Migrating an application from EWS to Graph isn't necessarily a simple configuration change.
Depending on the application, it may require:
- installing an updated version;
- changing the application's Microsoft 365 integration;
- changing authentication methods;
- updating permissions;
- obtaining an update from the software vendor; or
- modifying bespoke software.
This is why identifying dependencies early matters.
What should UK businesses do now?
Businesses don't need to panic or start changing Microsoft 365 settings at random.
They should establish whether they have an EWS dependency.
A sensible review would include identifying applications that interact with Exchange Online and determining whether those applications use EWS, Microsoft Graph or another supported connection method.
Where third-party software is involved, the software vendor should be able to confirm whether its current version is affected by Microsoft's EWS retirement.
Where bespoke software is involved, the organisation responsible for maintaining that application may need to review its Exchange integration.
And where Microsoft 365 is managed by an IT support provider, businesses should ask whether their environment has been checked for EWS usage.
Don't wait until October to investigate
The danger with changes such as the EWS retirement isn't usually Microsoft's own software.
It's the forgotten integration that's been quietly working for years.
A business may have an application installed long before its current employees or IT provider became involved. If it continues to work, there is often little reason for anybody to investigate how it communicates with Microsoft 365.
Until Microsoft changes something.
Finding that dependency now gives the organisation time to investigate the software, speak to its vendor and implement an alternative.
Discovering it because an important business process suddenly stops working in October is a much less attractive option.
Microsoft 365 continues to change
The EWS retirement is another example of why businesses should treat Microsoft 365 as an actively evolving cloud platform, rather than software that is configured once and forgotten.
Microsoft regularly changes security requirements, licensing, storage allowances, applications and features.
For Microsoft 365 customers, some changes provide additional functionality and capacity. Others, such as the EWS retirement, require organisations and their technology providers to check that older systems remain compatible.
You can also explore more practical Microsoft 365 and IT guidance in the KES IT Support Learning Centre.
Need help checking your Microsoft 365 environment?
If your business uses Microsoft 365 and you're unsure whether any applications or integrations could be affected by the retirement of Exchange Web Services, KES can help review your environment and identify areas that may require attention.
KES provides Microsoft 365 support and managed IT services for businesses, helping organisations manage licensing, security, users, devices and the wider technology their employees depend on.
Contact KES to discuss your Microsoft 365 environment or wider IT support requirements.
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