Starting February 1, 2027, the traditional phone and SMS authentication methods in Microsoft 365 will be discontinued. Therefore, please set up the Microsoft Authenticator app instead of using phone or SMS authentication going forward.
The OUMail service requires the use of the Microsoft Authenticator app. Although there are several ways to register for “Passkeys,” which Microsoft will begin recommending starting in September 2026, the setup process depends heavily on your individual usage environment—such as the devices and accounts you own—and is therefore not covered by our support. (Examples: whether you have purchased a physical security key, or whether you have a Google Account or Apple ID (iCloud).)
If you have not switched to the Microsoft Authenticator app by January 31, 2027, Microsoft will require you to register a “passkey” starting in February. Depending on your environment, you may not be able to register successfully. In that case, please review the section titled 【Reset of MFA(Multi-factor Authentication)】 at the top of the left-hand menu and follow the reset procedure. (Please set up the Microsoft Authenticator app after the reset.)
You can change your registered authentication method by accessing the following URL.
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Please access the following URL
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Click [Sign In Method] and add your authentication method.
If you currently use only phone or SMS authentication and would like to add the “Microsoft Authenticator” app, select the Microsoft Authenticator. Starting in September 2026, you may see an option labeled “Microsoft Authenticator Passkey,” but please do not select that option; instead, select “Microsoft Authenticator” as shown in the image below.
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For the remaining steps, follow the instructions in Section 2-1.Set up multi-factor authentication (using an authenticator app) of the MFA setup guide to complete the registration.
- Once you’ve confirmed that you can sign in using multi-factor authentication with the added authentication method (in this example, the “Microsoft Authenticator” app), you’re all set.
[Important Note]
If you switched to the app because phone and SMS authentication will be discontinued on January 31, 2027, please make sure you can sign in using the app, and then go to the security information screen mentioned above and “Delete” the phone (SMS) entry. (Microsoft recommends this as a way to streamline multi-factor authentication methods that are no longer needed.)