Microsoft has released Security Updates (SUs) for vulnerabilities found in:
Exchange Server Subscription Edition (SE)
Exchange Server 2019
Exchange Server 2016
SUs are available for the f...
Updated Aug 13, 2025
Version 4.0
Blog Post
Has been acknowledged by Microsoft 365. (Admin Center > Service Health)
Some on-premises users can't send or receive Exchange Online email messages on iOS and Android mobile devices
Issue ID: EX1138497
Affected services: Exchange Online
Status: Service degradation
Issue type: Advisory
Start time: Aug 20, 2025, 10:52 PM GMT+10
User impact
On-premises users can't send or receive Exchange Online email messages on iOS and Android mobile devices.
Scope of impact
Some on-premises users attempting to send or receive email messages on iOS and Android mobile devices may be impacted.
Current status
Aug 21, 2025, 1:54 AM GMT+10
While our review of service logging to identify the underlying cause of this event is ongoing, we're implementing a fix to alleviate the impact. We anticipate the fix will be deployed by our next scheduled communications update, at which time we'll monitor the service to confirm if it’s had any effect in remediating the impact.
Next update by:
Friday, August 22, 2025 at 3:30 AM GMT+10
does this problem affect only users with the MS Outlook mobile app or also users with other EAS apps like the native IOS or Google mail app?
I believe it is only the Outlook Mobile app as that uses the intermediate Outlookserver to connect from cloud to on-prem. Native IOS in hybrid auth mode connects directly to the on-prem exchange (other than for the OAuth token)