Outlook error 0x800CCC33 appears when the mail server refuses the login details Outlook sends, so messages get stuck in the Outbox or never arrive. It usually comes down to a wrong password, a missing authentication setting, or incorrect server details. The steps below fix each of those in the order most likely to work.
Key Takeaways
- Error 0x800CCC33 is an authentication failure, so the fix almost always involves the password or the outgoing server settings.
- Confirm the password works in webmail first, then re-enter it in Outlook.
- Turn on outgoing server (SMTP) authentication and match the port and encryption to the provider.
- Gmail, Yahoo, and similar providers often need an app password instead of the normal one.
- A fresh Outlook profile resolves most cases that survive the earlier steps.
How to Fix Outlook Error 0x800CCC33 Step by Step
These steps apply to classic Outlook for Windows (Microsoft 365, Outlook 2021, 2019, and 2016). Work through them in order and test by pressing Send/Receive after each one.
- Step 1: Open a browser and sign in to the email account through its webmail page. If the login fails there, the password is wrong or the account is locked, and resetting it with the provider is the real fix. Then continue with the new password.
- Step 2: In Outlook, go to File, then Info, then Account Settings, and choose Account Settings again. Select the failing account and click Change (or Repair if it is offered).
- Step 3: Re-enter the full email address and the correct password. If the provider uses two-step verification, enter an app password here instead of the regular password. Click Next, then Done.
- Step 4: Back in the Account Settings window, double-click the account and select More Settings. Open the Outgoing Server tab and tick the checkbox for outgoing server (SMTP) authentication. Choose ‘Use same settings as my incoming mail server’, then click OK.
- Step 5: Open the Advanced tab in the same More Settings window. Match the ports and encryption to the provider. The most common working combination is IMAP on 993 with SSL/TLS, and SMTP on 587 with STARTTLS (or 465 with SSL/TLS). For POP accounts, the incoming port is usually 995 with SSL/TLS.
- Step 6: Clear the saved credentials. Close Outlook, open Windows Credential Manager from the Start menu, select Windows Credentials, and remove every entry that starts with MicrosoftOffice16 or contains the mail server name. Reopen Outlook and sign in again when prompted.
- Step 7: Pause any antivirus or firewall email scanning for a few minutes and press Send/Receive. If the error disappears, add Outlook as an allowed program or switch off the email scanning feature permanently.
- Step 8: If nothing has worked, create a new profile. Close Outlook, open Control Panel, choose Mail (Microsoft Outlook), click Show Profiles, then Add. Set up the account again in the new profile and select it as the default.
Tip: Test the account in webmail before changing anything inside Outlook. It takes thirty seconds and instantly shows whether the problem is the account itself or only the Outlook settings.
Common Causes Behind Error 0x800CCC33
Wrong or Outdated Password
A password changed on another device or reset by the provider leaves Outlook sending old credentials. The server rejects them, and the error follows. This is the most common trigger, especially after a phone or webmail password change.
Outgoing Server Authentication Switched Off
Most providers refuse to relay mail unless the SMTP server confirms who is sending. If that checkbox is cleared, sending fails even when receiving works perfectly. A typical scenario: new messages download fine, but every reply sits in the Outbox.
Incorrect Ports or Encryption
A mismatch between the port and the encryption type causes the server to drop the connection before login finishes. Pairing port 587 with SSL/TLS instead of STARTTLS is a frequent example.
App Password Required
Providers such as Gmail and Yahoo reject the normal password in Outlook when two-step verification is on. A generated app password is needed instead.
Common Problems and Fixes
The Error Returns After Entering the Correct Password
Saved credentials are probably cached. Remove the matching entries in Windows Credential Manager (Step 6), restart Outlook, and sign in again.
Receiving Works but Sending Still Fails
The problem sits in the SMTP settings. Recheck the Outgoing Server tab for the authentication checkbox, then confirm the outgoing port and encryption on the Advanced tab.
The Change Button Is Missing or the Settings Look Different
The new Outlook for Windows uses a different settings layout without the More Settings dialog. Switch to classic Outlook with the toggle at the top right, or remove and re-add the account under Settings, then Accounts.
Stuck Messages Remain in the Outbox
Open the Outbox, delete or move the stuck message to Drafts, then resend it after the settings are fixed. A message that failed earlier does not always retry on its own.
Tip: After changing settings, close Outlook completely and reopen it before testing. Some changes only take effect on a fresh start.
Frequently Asked Questions
What does Outlook error 0x800CCC33 mean?
It means the mail server rejected the authentication details Outlook sent. The cause is usually a wrong password, disabled SMTP authentication, or mismatched server settings.
Is error 0x800CCC33 caused by a problem with the account itself?
Sometimes. A locked, suspended, or expired account triggers it, which is why signing in through webmail is the best first test.
Why can Outlook receive email but not send it?
Receiving uses the incoming server, while sending uses the SMTP server, which has its own authentication setting. If SMTP authentication is off or the outgoing port is wrong, sending fails while receiving keeps working.
Which SMTP port should be used to stop the error?
Port 587 with STARTTLS is the most widely supported choice. Port 465 with SSL/TLS also works with many providers. Check the provider’s own settings page for the exact combination.
Do Gmail accounts need an app password in Outlook?
Often yes, particularly when two-step verification is turned on. An app password generated in the Google account security page replaces the regular password in Outlook.
Can antivirus software cause this error?
Yes. Email scanning features can interfere with the connection to the mail server. Temporarily disabling that scanning shows whether the antivirus is responsible.
How can saved passwords be cleared for Outlook?
Open Windows Credential Manager, choose Windows Credentials, and remove the entries that begin with MicrosoftOffice16 or reference the mail server. Outlook then asks for the password again at the next sign-in.
Will creating a new Outlook profile delete emails?
For IMAP and Microsoft 365 accounts, mail stays on the server and downloads again into the new profile. For POP accounts, existing data files should be backed up first, since mail may be stored only on the computer.
