Can antivirus cause this error?

Yes. Email scanning features in Norton, Avast, and Kaspersky can intercept SMTP connections. Disable the email scanning module specifically, not the entire antivirus.

Why does receiving work but sending fails?

Receiving uses IMAP (port 993) or POP3 (port 995) which are different from SMTP. The issue is specific to the outgoing mail server configuration.

Outlook Error 0x800CCC0E — Cannot Connect to Mail Server

Warningapplication

Overview

Fix Outlook error 0x800CCC0E preventing email send/receive due to SMTP server connection failures, port blocking, or incorrect email account settings.

Key Details

Error 0x800CCC0E indicates Outlook cannot establish a connection to the outgoing SMTP mail server
Most commonly caused by incorrect SMTP port or server address configuration
Firewall or antivirus software may block Outlook's connection to email ports
SSL/TLS encryption settings must match the email provider's requirements
This error affects sending emails; receiving may still work via IMAP/POP3

Common Causes

Incorrect SMTP server address or port number in Outlook account settings
Firewall blocking port 587 (TLS) or 465 (SSL) for outgoing mail
Antivirus email scanning feature interfering with the SMTP connection
ISP blocking outgoing SMTP port 25 to prevent spam

Steps

1Verify SMTP settings: File > Account Settings > select account > Change > More Settings > Advanced tab
2Use port 587 with STARTTLS or port 465 with SSL/TLS for most providers (Gmail, Outlook.com, Yahoo)
3Temporarily disable firewall and antivirus email scanning to test the connection
4Run Outlook in safe mode: hold Ctrl while launching Outlook to disable add-ins
5Test SMTP connectivity: open Command Prompt and run 'telnet smtp.provider.com 587'