Exchange Web Services Is Being Retired

Microsoft is turning off Exchange Web Services in Microsoft 365. If Apptoto reaches your calendars through the Sync Agent and a Microsoft 365 mailbox, you need to move to a direct Microsoft 365 connection before April 2027.

What is changing

Exchange Web Services (EWS) is the older Microsoft interface that the Apptoto Sync Agent uses to read calendars and address books from an Exchange server. Microsoft is retiring it in Microsoft 365 on this schedule:

Date	What happens
End of August 2026	Last chance for a Microsoft 365 administrator to add an application allow list and keep EWS switched on past October. Tenants that do this are excluded from the October change.
October 1, 2026	Microsoft switches EWS off by default for any tenant that has not opted out. Apps using EWS stop working that day.
April 1, 2027	EWS is permanently shut off in Microsoft 365. No exceptions, and no way to turn it back on.

Microsoft’s own announcement is here: Exchange Online EWS, Your Time is Almost Up.

Does this affect me?

You are affected if the Apptoto Sync Agent connects to a Microsoft 365 mailbox. In the Sync Agent’s Exchange settings, that shows up as a server address like https://outlook.office365.com/EWS/Exchange.asmx.

You are not affected if you connected your calendar through Settings > Integrations by signing in with Microsoft. That connection does not use Exchange Web Services, and nothing about it changes.

You are not affected if the Sync Agent points at an Exchange server your own organization runs on-premises. Microsoft’s retirement applies to Microsoft 365 only.

What to do instead

For almost everything the Sync Agent is doing against Microsoft 365 today, there is a direct connection that is simpler, needs no software running on your network, and is not going away.

1. Connect Microsoft 365 directly. Go to Settings > Integrations and open the Office 365 / Outlook.com / Hotmail / Live.com section. Click Add Connection to connect a single account, or Add Admin Connection to cover your whole organization in one approval.

2. Add your shared calendars by email. On the new connection, click the arrow next to Add Calendar and choose Add Calendar By Email. Shared mailboxes, room and equipment calendars, coworkers’ calendars, and Microsoft 365 Group calendars all work this way. Full walkthrough: Shared, Resource, and Room Calendars.

3. Check the new calendars are syncing. Open Settings > Calendars and confirm you see a green status next to each newly added calendar.

4. Remove the old calendars and retire the Sync Agent. Once the new calendars are syncing, remove the Sync Agent versions from Settings > Calendars so you are not looking at each appointment twice. If the Sync Agent was only there for Microsoft 365, you can uninstall it.

Move your appointments over before removing anything

Remove the old calendars only after the new ones are syncing. Removing a calendar removes its appointments and their scheduled messages from Apptoto. If you are unsure about the order of operations, contact Apptoto Support and we will walk through it with you.

Public folder calendars

There is one case with no direct replacement. Calendars stored under Public Folders in Outlook do not have their own email address, so there is nothing to type into Add Calendar By Email, and Microsoft has said it will not offer a new way for applications to read public folders.

If Apptoto syncs a public folder calendar for you, that calendar needs to move before EWS shuts off. Ask your Microsoft 365 administrator to recreate it as one of these:

• A shared mailbox, which is the usual replacement and behaves the way most teams expect
• A Microsoft 365 Group, if the calendar belongs to a team that already has one

Both have an email address, so Apptoto connects them with Add Calendar By Email. Give yourself some lead time: moving calendar contents out of a public folder is a real migration, not a setting to flip.

Keeping EWS running while you migrate

If you cannot finish the move before October 1, 2026, your Microsoft 365 administrator can keep EWS switched on for a while longer by turning it on explicitly and listing the applications allowed to use it. Microsoft’s deadline for setting that up is the end of August 2026, and even then, everything stops on April 1, 2027.

If you need Apptoto’s application ID to add to that list, contact Apptoto Support and we will send it to you.

Troubleshooting

How do I tell whether my calendars use the Sync Agent?

Open Settings > Calendars. Sync Agent calendars show the device they sync through, and their sync status depends on that computer being on and running the agent. Calendars connected by signing in with Microsoft show up under the Microsoft connection instead, and do not mention a device.

My calendars are in Public Folders and I can’t move them yet

Contact Apptoto Support before October 1, 2026. We can talk through the options and, if your organization sets up an allow list, give you the application ID you need. Do not wait until the April 2027 shutdown, because there is no extension past that date.

Will my messages and history be lost when I switch?

Your contacts, message templates, settings, and message history stay put. What changes is where Apptoto reads your appointments from. Add the new calendars first, confirm they are syncing, then remove the old ones.