Why does Outlook keep asking for MFA even after I authenticate?

MFA loops occur due to: 1) Cached credentials in Credential Manager conflicting with fresh tokens, 2) Conditional Access policy requiring re-authentication on every sign-in, 3) Legacy authentication (basic auth) attempting to connect when modern auth is required, or 4) Token expiration set too aggressively. Clear credentials via Control Panel > Credential Manager and test with Outlook on Web to isolate the issue.

How do I fix MFA loop for Outlook desktop?

1) Close Outlook completely. 2) Open Control Panel > User Accounts > Manage your credentials. 3) Delete all Exchange Online and Office 365 entries under Windows Credentials. 4) Reopen Outlook and sign in fresh. 5) Verify modern authentication is enabled (File > Office Account > ensure 'Connected to Exchange' shows modern auth). 6) If still looping, create a new Outlook profile to rule out corruption.

What Conditional Access settings cause MFA loops?

CA policies with 'Require multi-factor authentication' on every sign-in without persistent browser sessions or 'Sign-in frequency: Every time' can create loops. Also, conflicting policies (one allows, another blocks) or device compliance requirements that aren't met will trigger repeated challenges. Set CA policy to Report-only mode temporarily to confirm it's the cause.

How do I create an app password for legacy email clients?

1) User signs into https://myapps.microsoft.com. 2) Click profile icon (top right) > View account. 3) Click Security tab > App passwords. 4) Generate a new app password for the specific app (e.g., 'Mail' or 'Outlook'). 5) Use this generated password instead of the user's real password in the legacy email client (IMAP, POP3, older Outlook versions). Note: App passwords only work if the account has MFA enabled.

Fix MFA Authentication Loop: Diagnosis & Relief

Identify Conditional Access conflicts, legacy authentication requirements, and token issues driving repeated MFA prompts.

⚠️ Business Consequence: Why This Matters

Financial Impact: User lockout = $150–$400 per user per day (no email access during loop)
Compliance Exposure: Users bypassing MFA via workarounds = authentication policy violations
Operational Risk: Help desk overwhelmed with MFA loop tickets (10–20+ per day)
Security Risk: Forced MFA disablement = entire org loses second-factor protection

Average diagnosis time: 5–10 minutes — prevents mass authentication failure.

⚡ TL;DR: Stop MFA Loop in 5-10 Minutes

What breaks: User completes MFA successfully, but Outlook/OWA immediately prompts for MFA again—infinite loop prevents access.
Confirm: Check Azure AD sign-in logs for "MFA required" or "Conditional failure" after successful authentication. Diagnosis time: 3-5 minutes.
Fastest fix: Clear cached credentials (Credential Manager), test with OWA to isolate Outlook desktop, or temporarily set CA policy to Report-only mode. Time to resolution: 5-10 minutes.
Decision matrix: Desktop Outlook only → Clear credentials + test modern auth. All clients → CA policy conflict. Legacy IMAP/POP3 → Create app password. Third-party add-ins → Disable and retest.
Rollback: If changing CA policy, use CA policy rollback to restore original state within 2 minutes.

MFA Loop Quick Reference

Time to diagnose: 5-10 minutes
Most common cause: Conditional Access policy conflict
Quick fix: Clear cached credentials in Outlook or use OWA instead
Severity: P2 (impacts individual, not system-wide)

What Users Report

MFA loop happens when the same authentication challenge repeats endlessly:

Outlook or Outlook on Web (OWA) asks for MFA
User completes MFA successfully
App asks for MFA again immediately (or within seconds)
Cycle repeats—user never gains access

When it started matters: Did this begin after a password reset? After a CA policy change? Note the timing for diagnosis.

Diagnostic Steps (5-10 minutes)

Step 1: Check Sign-In Logs

Go to Azure Portal > Azure Active Directory > Sign-in logs. Filter for the affected user from the last hour. Look at the Failure Reason column:

"MFA required": Conditional Access is demanding additional verification
"Conditional failure": CA policy is blocking the sign-in even after MFA
"Token has expired": The MFA token is too old to use

Step 2: Verify Modern Authentication

Outlook for Windows and Mac use modern authentication by default. Old versions or legacy protocols (IMAP, POP3) don't support MFA:

Outlook desktop: Check version. Update to latest monthly build if older than 3 months
Outlook on Web: Always supports modern auth. Try https://outlook.office.com to isolate the issue
IMAP/POP3: These cannot do MFA. If user needs it, create an app password instead

Step 3: Test with Clean Profile

Cached credentials can cause loops. Clear them and test:

Close Outlook completely
Go to Control Panel > User Accounts > Manage your credentials
Delete any Exchange Online entries
Reopen Outlook and sign in fresh

Fixes (Choose Based on Diagnosis)

Fix 1: Adjust Conditional Access Policy

When to use: Sign-in logs show "Conditional failure"

Go to Azure AD > Security > Conditional Access
Find the policy blocking the user
Change from "Enabled" to "Report-only" (temporary)
Wait 5 minutes and test. User should now access Exchange
Review the policy. Is it too strict? Exclude this user or adjust conditions
When confident, enable the policy and test again

Fix 2: Enable Modern Auth in Outlook

When to use: Outlook version is old or legacy auth is enabled

For Outlook 2016/2019: Ensure you're on latest version (monthly updates)
For Outlook 2013 or older: Upgrade to Outlook 2019 or Microsoft 365
Verify in Outlook: File > Office Account > This mailbox uses modern authentication

Fix 3: Create an App Password (Legacy Clients)

When to use: User needs IMAP/POP3 or is stuck with legacy client

User goes to https://myapps.microsoft.com (signed in)
Click profile icon (top right) > View account
Click Security tab > App passwords
Generate password for "Mail" and "Windows Server" (Outlook)
Use this password instead of real password in mail client

Note: Only works if user's account is MFA-enabled. Not compatible with all legacy apps.