As we have been announcing, Exchange Web Services (EWS) protocol is being turned off in Exchange Online. This protocol is used by various applications such as:
Apple Mail / Calendar on macOS
Cl...
Updated Oct 21, 2026
Version 3.0
Blog Post
One more thing that stops when EWS is turned off: free/busy, MailTips and calendar sharing with other Microsoft 365 tenants through an Organization Relationship or a Sharing Policy. People in the partner tenant can stop seeing your free/busy, MailTips and shared calendars. Your users still see theirs as long as EWS is on in the partner's tenant, so you may hear about it from the partner first.
With EWSEnabled set back to True these work until April 1, 2027, whatever is in EwsAllowedAppIDs, because they don't rely on app IDs. MS says both tenants need True for it to work both ways. Long term, you migrate them to Cross-Tenant Access Policy yourself. Calendar sharing there is still rolling out, expected by October 30 in the worldwide cloud: Cross-tenant Free/Busy, MailTips, and Calendar Sharing are moving to Cross-Tenant Access Policy | Microsoft Community Hub
I will believe that October 30th date when it is actually achieved, they have revised the completion date, multiple times and wasted lots of my time, trying to make something work that they said was released, when actually it wasn't, and then updated the blog post 5 days later with another date, without so much as an apology for wasting peoples time. Meanwhile Nino_Bilic replies here and quietly ignored mine and other peoples questions in the other blog post. It appears at the moment with EWS back on, only classic outlook works and not OWA or new outlook.
- Greg Taylor - EXCHANGE
Microsoft
"It appears at the moment with EWS back on, only classic outlook works and not OWA or new outlook." - not following what you mean here? Can you elaborate?
Hi, thank you for for replying Greg, when trying to open an external users calendar, classic outlook works (as long as you open it from one of the contact records that we have created). If I try and add any external calendars in OWA or outlook new via the contact record, they sometimes just add a blank calendar with no details, or do not add the calendar at all. Behind the scenes in a browser trace it is saying that you do not have access to this mailbox. If Itry adding someone via their email address in OWA/outlook new it puts a message at the bottom of the screen saying that it cannot add the calendar.
