Iphone indicates that outlook requires IOS 26. Currently up to date with IOS 18+

Update the iPhone XR to iOS 26 if Settings → General → Software Update offers it; if no compatible update appears, do not delete the existing Outlook app because the App Store may not let you reinstall it on iOS 18.

Microsoft optimizes Outlook for only the latest two iOS versions, and the current App Store release requiring iOS 26 places iOS 18 outside that window.^1^ Apple states that Software Update offers only releases compatible with the particular iPhone model.^2^

Check the available iOS update

1. Back up the iPhone.
2. Open Settings → General → Software Update.
3. If iOS 26 is offered, connect to power and Wi-Fi, install it, and then update Outlook from the App Store.
4. Restart Outlook and sign in using the new password.

If iOS 26 is not offered, the phone cannot install the current Outlook release through the normal supported update path. Continue using the installed version for now, or access the mailbox through Outlook on the web in Safari. A device capable of running a supported iOS release is the long-term option.

Do not uninstall Outlook merely to troubleshoot it while the App Store requires a newer iOS version; reinstalling may be unavailable.

Treat today’s connection error separately

Because Outlook still works on the HP desktop and the mobile failure began suddenly, check Microsoft’s public service status page:

https://portal.office.com/servicestatus/

Expand Microsoft consumer products, then check Outlook.com. Similar sudden iOS connection failures have occurred during wider Outlook connectivity incidents.^3^ If an incident is listed, wait for service restoration rather than changing the password again.

The available guidance does not provide a verified Outlook-app account-reset menu path for this exact version, so deleting the account or app should not be the next step while reinstallability is uncertain.

If the error is actually in Apple Mail

If “Unable to connect to server” appears in Apple’s built-in Mail app rather than Microsoft Outlook, re-add the account using modern authentication:

1. Open Settings → Apps → Mail → Mail Accounts
   (on some iOS versions: Settings → Mail → Accounts).
2. Select the Outlook/Hotmail account and tap Delete Account. This removes it from the iPhone, not from Microsoft’s servers.
3. Return to Mail Accounts → Add Account.
4. Choose Outlook.com—do not configure it manually as POP or IMAP.
5. Sign in with the new password and complete any verification prompt.

Choosing Outlook.com configures OAuth authentication and addresses connections previously configured with outdated basic authentication.^4^

References

1. What version of iOS does your app support? | Microsoft Support
2. How to download iOS 26 - Apple Support
3. Mail app cannot connect to hotmail account - Microsoft Q&A
4. Outlook and other apps are unable to connect to Outlook.com when using Basic authentication | Microsoft Support