0x800CCC0E
Outlook error 0x800CCC0E: cannot connect to server
Outlook reports 0x800CCC0E when it cannot open a connection to the mail server. Usually a wrong port, blocked TLS, or a firewall — rarely Outlook itself.
- Applies to
- Outlook for Microsoft 365, Outlook 2019 / 2021
- Updated
- Read time
- 1 min
What the error means
Outlook tried to connect to an SMTP, IMAP, or POP server and the TCP or TLS handshake failed. Exchange Online and Outlook.com accounts rarely see this; it's almost always a third-party or on-premises mail server.
Test the connection first
Test-NetConnection mail.example.com -Port 587
Test-NetConnection mail.example.com -Port 993
TcpTestSucceeded : False means it's a network problem, not Outlook.
Check the account settings
File → Account Settings → Server Settings
| Protocol | Port | Encryption |
|---|---|---|
| IMAP | 993 | SSL/TLS |
| POP3 | 995 | SSL/TLS |
| SMTP | 587 | STARTTLS |
| SMTP | 465 | SSL/TLS |
A mismatch — such as port 465 with STARTTLS — produces this error.
Other causes
- Antivirus email scanning intercepting the connection. Disable it temporarily to test.
- TLS 1.0/1.1 only servers. Current Outlook builds require TLS 1.2+.
- Corrupt profile. Create a new one under Control Panel → Mail → Show Profiles.
Verify
Send a test message with File → Account Settings → Repair, or use Test Account Settings in the advanced dialog.