Outlook 0x80049DDE OAuth token expired fix

You're trying to send an email and Outlook throws error 0x80049DDE. I know that feeling. The send button does nothing, the outbox fills up, and you're stuck. The real fix is simpler than you'd think — it's just a stale OAuth 2.0 token that needs to be cleared out.

The Fix: Clear the Stored OAuth Token

This takes about two minutes and doesn't require admin rights on your computer. The fix works across Outlook 2016, 2019, 2021, and Microsoft 365 versions.

1. Close Outlook completely. Make sure it's not running in the system tray. Check Task Manager if you're not sure.
2. Open Control Panel (search for it in the Start menu).
3. Click User Accounts, then click Credential Manager on the left side.
4. Click Windows Credentials.
5. Scroll down to Generic Credentials. You'll see a bunch of entries here. Look for anything related to Microsoft Office or Outlook. Specifically, look for entries that start with MicrosoftOffice16_Data:ADAL: or MicrosoftOffice16_Data:MSOL:. On older versions, it might say MicrosoftOffice15_Data:ADAL:.
6. Expand each of those entries by clicking the arrow on the right. You'll see the full URL or resource name. The ones tied to your work or school email are your target.
7. Click Remove next to each one. Windows will ask you to confirm — click Yes.
8. After you've removed them all, close Control Panel.
9. Restart Outlook. It'll prompt you to sign in again. Enter your email and password. Depending on your organization's settings, you might get a multi-factor authentication (MFA) prompt. Complete that.
10. After signing in, try sending an email. It should go through now.

What you should see: After removing the credentials and restarting Outlook, you'll see a sign-in window pop up. That's good. Once you authenticate, the Send/Receive status at the bottom should show "Connected" and your outbox will clear.

What If You Don't See Sign-In Prompt?

Sometimes Outlook doesn't prompt you after removing credentials. If that happens:

• Go to File > Office Account (or Account in newer versions).
• You'll see your connected accounts listed. Click Sign Out next to the problematic account.
• Then click Sign In and re-enter your credentials.

Why This Works

Outlook 2016 and later use OAuth 2.0 for modern authentication with Microsoft 365 accounts. This is actually a good thing — it's more secure than the old basic auth. But here's the catch: OAuth tokens have an expiration time, typically 90 days. When that token expires, Outlook doesn't always prompt you to refresh it. Instead, it sits there with a stale token and throws 0x49DDE when you try to send.

The stored credentials in Windows Credential Manager contain that expired token. By removing them, you force Outlook to request a brand new token from Microsoft's servers. It's like clearing the jam before loading fresh paper.

You'll see entries like MicrosoftOffice16_Data:ADAL:3a6f9-...@outlook.com. The ADAL part stands for Active Directory Authentication Library — that's the OAuth 2.0 token cache. Removing these specific entries is the only way to guarantee a clean refresh.

Less Common Variations of This Problem

Multiple Credential Entries for the Same Account

Some users find two or three entries for the same email address — one for Outlook desktop, one for Teams, one for OneDrive. If you're still getting the error after removing just one, go back and check for duplicates. Remove them all.

Token Issue in Outlook for Mac

On Outlook for Mac, the fix is different. Go to Tools > Accounts, select your account, click the minus sign to remove it, then re-add it. The Mac version stores tokens in the Keychain. You could also open Keychain Access and search for "Exchange" or "Office" and delete relevant entries, but re-adding the account is more reliable.

Shared Mailbox or Delegated Access

If you have a shared mailbox or delegate permissions to another user's mailbox, the token for that secondary mailbox might expire independently. You'll see the same error when trying to send as that shared mailbox. The fix is the same — clear the credentials — but you'll need to look for credential entries tied to the shared mailbox's email address.

Conditional Access Policies from IT

Some organizations have conditional access policies that require re-authentication every 14 or 30 days. If your IT team set that up, your token expires faster. The credential removal fix still works, but you'll hit this more often. Talk to your IT admin about extending the token lifetime or adding your device to the trusted list.

How to Stop This From Happening Again

You can't completely prevent token expiration — Microsoft controls that. But you can reduce how often it catches you off guard.

1. Keep Outlook running. If you close Outlook for weeks at a time, the token sits unused and expires. Let it run in the background. Outlook refreshes tokens automatically when it's open and connected.
2. Make sure your system time is correct. OAuth tokens are time-sensitive. If your computer's clock is off by more than a few minutes, the token validation fails. Right-click the clock > Adjust date/time and turn on Set time automatically.
3. Update Outlook regularly. Old versions have bugs where token refresh doesn't trigger properly. Run Windows Update or Microsoft 365 updates monthly.
4. Use the latest Outlook version. Outlook 2016 and 2019 are fine, but Outlook for Microsoft 365 gets the most fixes for authentication issues. If you're on an old standalone version, consider upgrading.

If you see error 0x80049DDE again in the future, now you know the drill. Remove the expired token from Credential Manager, restart Outlook, sign back in. That's it. You don't need to repair Office, run a scan, or reinstall anything. Just clear the credentials and move on.