Outlook error 0x800CCC79 in Windows usually shows up while sending or receiving mail, and it stops messages from leaving the outbox. It typically points to a server authentication issue, a blocked connection, or a mismatched port setting. The steps below walk through the fixes that actually resolve this error, in the order most likely to work first.
Key Takeaways
- Error 0x800CCC79 almost always relates to SMTP authentication, port settings, or a blocked connection.
- Re-entering account credentials and confirming server settings fixes the majority of cases.
- Antivirus email scanning and Windows Firewall are common hidden culprits.
- A quick profile repair or recreation clears cases that settings alone do not fix.
- Keeping Outlook updated prevents this error from returning after certain patches.
Step-by-Step Guide to Fix Outlook Error 0x800CCC79
Work through these steps in order. Most users find the fix within the first four steps, but the later ones matter for stubborn cases.
- Step 1: Open Outlook and go to File, then Account Settings, then Account Settings again. Select the affected email account and click Change.
- Step 2: Re-enter the account password exactly, even if it looks correct. A saved password that has expired or changed on the mail server’s side is one of the most common triggers for this error.
- Step 3: Under More Settings, open the Outgoing Server tab and confirm ‘My outgoing server (SMTP) requires authentication’ is checked, with ‘Use same settings as my incoming mail server’ selected unless the provider specifies otherwise.
- Step 4: Switch to the Advanced tab and check the port numbers for the incoming and outgoing servers. Compare them against the settings published by the email provider, since a wrong port number is a frequent cause of this exact error.
- Step 5: Increase the server timeout. On the same Advanced tab, drag the ‘Server Timeouts’ slider closer to the Long end. A short timeout is a common trigger on slower connections or larger mailboxes.
- Step 6: Temporarily disable email scanning inside the antivirus software. Security suites that intercept SMTP traffic can block the connection Outlook is trying to make, producing this same error code.
- Step 7: Check Windows Firewall to confirm Outlook is not being blocked. Go to Windows Security, then Firewall & network protection, then Allow an app through firewall, and verify Outlook has both Private and Public access checked.
- Step 8: Send a test email once settings are updated. If the error returns, move to profile repair below.
Tip: Write down the original port numbers and timeout value before changing anything, so settings can be reverted quickly if a step does not help.
Repairing or Recreating the Outlook Profile
When the steps above do not clear the error, the account profile itself may be the problem. This works best when other fixes have already ruled out server settings.
- Step 1: Close Outlook completely.
- Step 2: Open Control Panel and search for Mail (Microsoft Outlook).
- Step 3: Click Show Profiles, select the current profile, and click Properties, then Email Accounts, then Repair for the affected account.
- Step 4: If the repair does not resolve the error, create a new profile instead. In the same Mail window, click Add, follow the prompts to set up the account again, and set the new profile as default.
- Step 5: Open Outlook with the new profile and test sending and receiving mail.
Common Problems and Fixes
Error Returns Only When Sending Large Attachments
This usually points to a server timeout that is still too short, or an attachment size limit set by the mail provider. Increase the timeout again and confirm the attachment falls within the provider’s stated size limit.
Error Appears Right After a Password Change
Outlook sometimes keeps using a cached password. Delete the saved password in Account Settings under More Settings, then re-enter it manually so Outlook stores the current one.
Error Only Happens on One Network
Some workplace or public networks block outgoing SMTP traffic on the default port. Contact the mail provider for an alternate port number, often 587 with SSL/TLS, and update it under the Advanced tab.
Error Persists After Reinstalling Outlook
A corrupted Outlook data file can survive a reinstall. Run the Inbox Repair Tool (scanpst.exe), located in the Outlook installation folder, against the affected .pst or .ost file.
Antivirus Keeps Re-Blocking the Connection
If disabling email scanning fixes the error temporarily but it returns, add Outlook as a trusted application inside the antivirus software instead of leaving scanning off entirely.
Frequently Asked Questions
What does Outlook error 0x800CCC79 actually mean?
It means Outlook was blocked from relaying or sending a message through the SMTP server, usually because of authentication, port, or connection restrictions.
Is 0x800CCC79 caused by a virus?
No. It is a connection or authentication error, not a sign of malware, though antivirus software can trigger it by interfering with the email connection.
Does this error affect incoming mail too?
It typically affects outgoing mail only, since it relates to the SMTP send process rather than the POP3 or IMAP retrieval process.
Which port should the SMTP server use?
Most providers use port 587 with SSL/TLS or port 465 with SSL, but the exact port depends on the email provider, so check its official settings page.
Will creating a new Outlook profile delete existing emails?
No, as long as the mailbox is stored on the mail server (as with most IMAP and Exchange accounts) or the existing .pst file is reconnected during setup.
Can a VPN cause this error?
Yes. Some VPNs block or reroute SMTP traffic, which can produce this exact error. Try disconnecting the VPN and testing again.
How long should the server timeout be set to?
Somewhere between 3 and 5 minutes works for most connections. Slower networks may need it closer to 5 minutes.
Does updating Outlook fix this error?
In some cases, yes. Microsoft periodically patches connection handling bugs, so running Outlook on its latest update can resolve error instances tied to those bugs.
Why does the error only happen at certain times of day?
This often points to server-side congestion or rate limiting on the provider’s end rather than a local Outlook setting, especially if the error clears on its own after a short wait.
