Outlook mobile authentication was unsuccessful

Question

Outlook mobile authentication was unsuccessful

Brody McCulloch 0

Hi all,

Looking for help with is error.

Using Outlook app for IOS.

I have tried to remove and reset the account. I have also removed the account from the authentication app.

Emails work, but the banner keeps popping up.

0 comments

2 answers

Your answer

Answer 1

Hello @Brody McCulloch,

This usually happens when the authentication token on the device is out of sync, even though the mailbox is still able to send and receive.

You’ve already tried removing the account, but there are a few additional steps that may help fully clear the issue you may want to try again:

Remove the account from all places on the phone

Outlook app
iOS Settings > Mail > Accounts
Microsoft Authenticator (delete the account entry there)

Delete the Outlook app completely from the phone
Restart the device (important to clear cached credentials)
Reinstall Outlook from the App Store
Add the account again

Make sure you sign in through the Microsoft sign-in page
Approve the MFA prompt when it appears

After adding, check that there are no duplicate accounts (for example, the same email added as both personal and work)

As you're using an iOS device, you can follow the official instruction from Apple Support to remove and add the email account to your device correctly:

(Note: This link is shared by community members for your convenience. It points to a third-party site that is not managed or verified by Microsoft. We can’t guarantee the quality, safety, or suitability of any content or software found there. Please review carefully and make sure you understand any potential risks before using it.)

You can also ask your organization's Microsoft 365 Admin to revoke your MFA access and try setting up your Authenticator again. Ask your admin to:

Go to Microsoft Entra Admin Center: https://entra.microsoft.com
Navigate to Entra ID > Users > All Users.
Select your user account.
Go to Authentication Methods.
Click "Require re-register multifactor authentication".

If the issue still persists after this, it may be related to a policy or conditional access setting on the tenant side. In that case, it’s worth having an admin check the sign-in logs for failed authentication attempts. Please provide your admin with these instructions as references:

If you have any trouble performing these steps, please feel free to leave a comment. I'll be happy to assist further!

Thank you again for reaching out!

Note: Please follow the steps in our documentation to enable e-mail notifications if you want to receive the related email notification for this thread.

Tamara-Hu 16,860 Reputation points Microsoft External Staff Moderator

2026-05-29T14:39:31.8466667+00:00

Hello @Brody McCulloch,

I hope you're having a nice day! I wanted to follow up to see if you need any additional help. I hope everything is going well on your part.

If you have any doubts, need clarification, or new questions have arisen, don't hesitate to get in touch. I am here to support you and happy to help.

Your satisfaction is important to me, and I want to make sure you feel safe and supported throughout the process. Just tell me how I can help you more.

I look forward to hearing from you!
Brody McCulloch 0 Reputation points

2026-05-30T21:36:37.94+00:00

Hello, our IT provider completely wiped the authentication and it fixed the problem.

Thanks for following up.
Tamara-Hu 16,860 Reputation points Microsoft External Staff Moderator

2026-06-02T07:26:52.96+00:00

Hello @Brody McCulloch,

Thanks for your confirmation. I'm glad your issue is resolved!

If you think my answer is helpful, you can click "Accept Answer". This will help users with similar problem find solution to their issue more easily. Your contribution is much appreciated!

In the meantime, I’ll continue monitoring other customer inquiries on the forum to ensure everyone receives timely support. If you have any updates or further questions, feel free to tag me in your reply so I can assist you more directly.

Or you can create another thread if you encounter any new issue. We'll be happy to assist!

Thank you and I wish you a great day!

Answer 2

The error indicates that Outlook for iOS cannot complete the sign‑in/authentication flow for the account being used.

Based on the available guidance, use these steps depending on the account type and how Outlook is being used to authenticate:

If Outlook mobile is being used as a sign‑in verification method (MFA)
1. Open Outlook on the phone.
2. Go to Settings → Accounts → [the affected account] → Account → Sign‑in requests.
3. Turn Allow sign‑in requests off, then on again to re‑enable Outlook as an authentication method.
4. If Outlook was previously removed as a sign‑in method, re‑add it by following the same path and enabling Allow sign‑in requests.
5. If sign‑in verification still fails, switch to Microsoft Authenticator instead, as that is the supported app for personal accounts and also works for work/school accounts.
If unable to sign in to the mailbox in Outlook for iOS at all
1. Confirm that the account credentials are valid by signing in to the account’s web portal (for example, Outlook on the web/OWA or the provider’s webmail).
2. If this is a Microsoft personal account and sign‑in fails or repeatedly prompts for a password, run the online sign‑in helper from the Can’t sign in to the Outlook mobile app article to detect and fix account issues, then try adding the account back in Outlook for iOS.
3. If this is a work or school (Microsoft 365) account and the password is forgotten or not accepted, reset it using the Reset password link in the same article (if self‑service password reset is enabled) or contact the organization’s IT admin.
4. For non‑Microsoft accounts (Gmail, iCloud, Yahoo, etc.), follow the provider’s sign‑in troubleshooting guidance and ensure any required app‑specific passwords or 2‑step verification settings are correctly configured, then re‑add the account in Outlook for iOS.
If Outlook mobile is blocked by account security/MFA configuration
1. If multi‑factor authentication methods are misconfigured (for example, the old phone was reset or removed), ask a tenant/global admin to require re‑registration of MFA so that new methods can be set up, then sign in again in Outlook.
2. If the affected account is the only admin in the tenant and cannot pass MFA, contact Microsoft support (Data Protection team) via the regional support phone number so they can verify identity and help regain access.

If, after these steps, Outlook for iOS still shows “Outlook authentication was unsuccessful,” the next step is to work with the account’s provider or the organization’s IT/admin support, as they control the account’s sign‑in and MFA configuration.

References: