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Windows PC Errors

How to Fix Outlook Error 0x800CCC0F (Send/Receive Connection Failed)

By ErrorFix · Updated October 17, 2026 · 6 min read

Error 0x800CCC0FPlain English: Outlook was in the middle of sending or receiving when your mail server hung up the connection. Your emails are safe — the conversation between the app and the server just got cut off, usually by antivirus software or wrong port settings.
Quick answer: Temporarily turn off your antivirus email-scanning feature and Windows firewall, then press Send/Receive. If the error is gone, you have found the culprit. Otherwise raise the Server Timeouts slider in File, Account Settings, Account Settings, Change, More Settings, Advanced — and double-check your port and encryption numbers.

What 0x800CCC0F means

You press Send/Receive and Outlook pops up a dialog: Your server has unexpectedly terminated the connection. Possible causes for this include server problems, network problems, or a long period of inactivity. Account: (your account), Protocol: POP3, Port: 110, Secure(SSL): No, Error Number: 0x800CCC0F. Nothing sends, nothing downloads, and anything already in the Outbox stays there. If you keep clicking Send/Receive, the same dialog keeps returning.

The wording is scarier than the reality. Your account is almost certainly fine — open the same mailbox in a web browser and everything works normally, messages send and arrive. That tells you the emails, the password, and the server are all healthy. The failure is local: something on your PC interrupts the connection between Outlook and the mail server, or the server rejects the connection because Outlook is knocking on the wrong door. The fixes below find which one it is, starting with the most common offender.

Common causes

How to fix Outlook error 0x800CCC0F — step by step

Work through these fixes in order. The antivirus test in step 2 resolves it for most people.

  1. Wait a few minutes, then retry and check webmail The error message itself names server problems as the first possible cause, so rule that out before changing anything. Close the error dialog, wait five minutes, and press Send/Receive again — maintenance and brief outages clear on their own. In the meantime, open your account in a web browser. If webmail sends and receives normally, your account is healthy and the problem is strictly between Outlook on your PC and the server.
  2. Temporarily disable antivirus email scanning and the firewall Email-scanning features in antivirus programs are the single most common trigger for 0x800CCC0F: they intercept Outlook's connection to the mail server, and the server hangs up on the tampered session. Open your antivirus settings and turn off email scanning, mail shield, or anti-spam for a test. Then go to Settings, Privacy and Security, Windows Security, Firewall and network protection, and briefly turn off the firewall on your active network. Run Send/Receive. If the error is gone, re-enable both protections and add outlook.exe and your Outlook data file folder to the antivirus exclusions instead of leaving anything off.
  3. Increase the server timeout setting When a sync runs long — a big attachment, a full mailbox download — the server can drop the connection before Outlook finishes, producing exactly this error. In Outlook, go to File, Account Settings, Account Settings, select your account, and click Change. Click More Settings, open the Advanced tab, and find the Server Timeouts slider. Drag it toward Long (around 2 to 5 minutes), click OK, then Next and Finish. Press Send/Receive and confirm the long-running sync now completes.
  4. Verify your incoming and outgoing ports and encryption Wrong ports or a mismatched encryption setting will get the connection refused or terminated every time. Back in More Settings, Advanced tab, confirm the values your provider requires: for POP3 use port 110 without encryption or 995 with SSL, for IMAP use 143 without encryption or 993 with SSL, and for SMTP use 25 or 587 with STARTTLS (or 465 with SSL). Compare against the official values on your email provider's help page — providers change them occasionally, and one wrong number is enough to cause 0x800CCC0F.
  5. Match the outgoing server authentication settings In More Settings, open the Outgoing Server tab. Tick My outgoing server (SMTP) requires authentication and select Use same settings as my incoming mail server — most providers demand this, and without it the send side gets terminated. While you are here, check the Advanced tab's Log on using Secure Password Authentication box: it must match what your server expects. If your provider does not use Secure Password Authentication, an enabled SPA checkbox will kill every connection — uncheck it and test again.
  6. Repair the data file with SCANPST A corrupted data file can abort a sync mid-way and present as a connection failure. Close Outlook completely — check Task Manager and end any outlook.exe process. Press Windows key plus R, paste %programfiles%/Microsoft Office/root/office16 into the Run box, and press Enter (on older Office use office15), then double-click SCANPST.exe. Click Browse, select your OST or PST file, and click Start. If it finds errors, tick Make backup of scanned file before repairing and click Repair. Open Outlook afterward and run Send/Receive to confirm the connection now completes.

Did this fix it? Quick checklist

If the error persists after all six steps, try sending from a different network — a mobile hotspot rules out router or ISP interference. Disable any Outlook add-ins from File, Options, Add-ins in case a broken add-in is hijacking the connection. As a last resort, create a brand-new Outlook profile (Control Panel, Mail, Show Profiles, Add) and let the account set itself up fresh — a corrupted profile's hidden settings can cause connection failures nothing else explains.

Frequently asked questions

What does Outlook error 0x800CCC0F mean?

The full message reads: Your server has unexpectedly terminated the connection. Possible causes for this include server problems, network problems, or a long period of inactivity. In plain terms, Outlook was mid-conversation with your mail server when the server hung up. Your account and your emails are fine — the conversation between the app and the server got interrupted.

Why does 0x800CCC0F keep coming back on every Send/Receive?

Recurrence means a persistent configuration issue, not a blip. The usual repeat offenders are an antivirus email shield intercepting every connection, a wrong port or encryption setting that the server rejects on each attempt, or a Secure Password Authentication checkbox that does not match the server. Walk the steps above in order — the cause almost always shows up by step 5.

Will disabling my antivirus to test leave me unprotected?

Only turn off the email-scanning feature, and only for the few minutes the test takes. Your real-time file and web protection stays on, and webmail still works during the test. If the test proves the antivirus is the blocker, re-enable everything and add outlook.exe plus your Outlook data file folder to its exclusions — you stay protected and Outlook connects cleanly.

What are the correct Outlook ports for POP3, IMAP, and SMTP?

Standard values are: POP3 port 110 without encryption or 995 with SSL; IMAP port 143 without encryption or 993 with SSL; SMTP port 25 or 587 with STARTTLS, or 465 with SSL. Always confirm against your provider's own help page, since some providers use custom ports — a single wrong number reproduces 0x800CCC0F on every send and receive.

I only get 0x800CCC0F when sending large attachments — why?

Big attachments make the upload run long, and the server drops idle or slow connections before it finishes — the long period of inactivity part of the error message. Drag the Server Timeouts slider toward Long as described in step 3, and try sending the file outside peak hours. If it still fails, upload the file to a cloud drive and email the link instead.

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