Microsoft is raising the minimum operating-system requirement for Outlook on iPhone and iPad. From September 2026, Outlook mobile will support only iOS 26 and iOS 27, along with the equivalent two newest versions of iPadOS and watchOS.
The important point is that Outlook will not suddenly delete anyone’s email or stop working on every older iPhone on one fixed day. Devices running iOS 18 or earlier will stop receiving Outlook updates. Microsoft says the last compatible version may continue to work for a time, but email and calendar synchronisation could eventually stop.
Microsoft first published the change in Message Center announcement MC1462923 on 27 August 2026. Rollout is due to begin in mid-September and complete by late September 2026.
What has Microsoft announced?
Following the general release of iOS 27, Microsoft will support Outlook mobile on only the two most recent Apple operating-system generations:
- iPhone: iOS 26 and iOS 27
- iPad: iPadOS 26 and iPadOS 27
- Apple Watch: watchOS 26 and watchOS 27
Outlook will no longer receive app updates on iPhones and iPads running version 18 or earlier. Support for watchOS 11 will also end.
This is a confirmed Microsoft announcement, not a rumour. Microsoft says the change is intended to keep Outlook aligned with the latest Apple platforms for performance, reliability and security.
Will Outlook stop working immediately in September?
No—not necessarily. Microsoft says users on iOS 18 can continue using the last supported version of Outlook. The app is not expected to switch off instantly when the support policy changes.
However, an unsupported Outlook version will no longer receive new features, bug fixes or compatibility updates. Microsoft also warns that, over time, it may stop synchronising email and calendar data.
That makes this a support deadline rather than a guaranteed outage date. Waiting until mail stops arriving would create unnecessary business risk, particularly for directors, remote workers and staff who depend on their phone for calendar alerts or urgent email.
Which older iPhones are affected?
The first check is the operating-system version, not simply the age of the phone. Any iPhone already running iOS 26 or later is unaffected by this change.
Apple’s official compatibility list shows that iOS 26 supports the iPhone 11 family and newer, plus the iPhone SE (2nd generation) and SE (3rd generation). Those models can remain supported by updating to iOS 26, even if they do not all receive every newer Apple feature.
Models that cannot move beyond iOS 18 include the iPhone XR, iPhone XS and iPhone XS Max, along with earlier iPhones. Outlook may continue running on its last compatible app version initially, but those devices cannot meet Microsoft’s new minimum requirement.
A newer supported iPhone can also be affected if its owner has simply postponed operating-system updates. In that case, the answer may be an update rather than a replacement device.
What about iPads and Apple Watches?
The same two-version support policy applies to iPadOS and watchOS.
Microsoft says support will end for Outlook on iPadOS 18 and watchOS 11. Apple’s iPad compatibility list is less straightforward because several generations and screen sizes overlap, so businesses should check the exact model rather than judging by appearance.
For Apple Watch, Apple lists watchOS 26 support from Series 6 onwards, including Apple Watch SE (2nd generation) and the Ultra models. Older watches that cannot install watchOS 26 will no longer be within Outlook’s supported range.
This does not affect Outlook on Windows, Mac or Android. It is specifically a change to Microsoft’s support requirements for Apple mobile devices.
How to check your iPhone or iPad
- Open Settings.
- Select General.
- Select About to see the model name and current iOS or iPadOS version.
- Go back and select Software Update.
- If iOS 26 or later is available, install it after making sure the device is backed up and has sufficient battery and storage.
If the device says it is up to date but remains on iOS 18, check the exact model against Apple’s iOS 26 compatibility list. It may be too old to receive the newer operating system.
On a business-managed device, updates may be controlled by your IT provider. Speak to them before resetting, replacing or removing any management profile.
Microsoft 365 Management
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- Microsoft 365 health and licence reviews
- Managed iPhone and iPad visibility
- Outlook and mobile email support
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Start a Microsoft 365 assessment →What should businesses do before September?
- Identify devices on iOS or iPadOS 18 and watchOS 11. Managed-device reports can help, but remember personally owned phones used for work may not appear there.
- Ask users to update compatible devices. A current iPhone that has fallen behind may need only a software update.
- Plan replacements for devices that cannot install iOS 26. Avoid waiting until Outlook synchronisation becomes unreliable.
- Check critical mobile users first. Prioritise directors, field staff, on-call employees and anyone who relies heavily on calendar reminders.
- Review bring-your-own-device arrangements. Decide who is responsible when a personal phone can no longer run supported business software.
- Do not remove security controls to keep an old device connected. Compatibility pressure is not a good reason to weaken mobile access policies.
For wider guidance, read our Microsoft 365 security hardening guide or compare Microsoft 365 Business Basic, Standard and Premium.
Quick answers
When does Outlook require iOS 26?
Microsoft plans to begin the change in mid-September 2026 and complete it by late September, following the general release of iOS 27.
Will email stop on the deadline day?
Microsoft does not say that all older devices will stop immediately. The last compatible Outlook version may keep working, but it will no longer receive updates and may eventually stop syncing email and calendars.
Does an iPhone 11 need replacing?
Not for this reason alone. Apple lists the iPhone 11 family as compatible with iOS 26, which remains within Microsoft’s supported range.
Which iPhones cannot meet the new requirement?
Apple’s iOS 26 list begins with iPhone 11 and iPhone SE (2nd generation). The iPhone XR, XS, XS Max and earlier models cannot install iOS 26.
Is Microsoft 365 licensing changing?
No. This announcement changes Outlook mobile’s supported Apple operating systems; it does not change Microsoft 365 licence entitlements.
The important point
This is an early warning, not evidence of an immediate Outlook outage. Affected users should update compatible devices now and replace only those that cannot move to a supported Apple operating system.
For SMEs, the hidden risk is not usually one centrally managed company phone. It is the older personal iPhone or iPad a key employee still uses for email, MFA prompts and calendars. Finding those devices before September is easier than troubleshooting missing messages after support has ended.
Sources
- Microsoft 365 Message Center MC1462923: Outlook for iOS minimum system requirements updated to iOS 26 and above (published 27 August 2026; Microsoft 365 administrator sign-in may be required).
- Public archive of Microsoft Message Center announcement MC1462923.
- Apple: iPhone models compatible with iOS 26.
- Apple: iPad models compatible with iPadOS 26.
- Apple: Apple Watch models compatible with watchOS 26.
Microsoft 365 rollout dates can change. This article reflects Microsoft’s published position on 29 August 2026 and should be rechecked against the current Message Center notice before publication.
