Some errors are simple and can be fixed with basic troubleshooting, while others may require advanced solutions. This guide provides a comprehensive list of common Outlook error codes along with their meanings and possible fixes. Whether you’re an IT professional or an everyday user, this resource will help you navigate Outlook issues with confidence.
IMAP and POP3
An error occurred with the subject ‘test‘.
Account: ‘mail.domain.com’, Server:’mail.domain.com’, Protocol: SMTP,
Server Response: ‘550 External MTA’s must be authenticated in order to send e-mails’, Port: 25, Secure(SSL): No, Server Error: 550.
Action: Ensure “Outgoing Server Requires Authentication” is checked.
IMAP and POP3
The connection to the server failed.
Account: ‘mail.domain.com’,
Server:’mail.domain.com’, Protocol: SMTP,
Port: 255, Secure(SSL): No, Socket Error: 10061.
Action: Port 255 is incorrect. Use Port 25 or 26.
IMAP
The server rejected your login. Please check your username and password.
POP3
There was an issue logging into your mail server. Password was rejected.
Account: ‘mail.domain.com’, Server:’mail.domain.com’, Protocol: POP3,
Server Response: ‘-ERR Login failed.’,
Port: 110, Secure(SSL): No.
Action: Ensure you’re using the full email address as the username. If needed, reset your password.
IMAP
The host ‘mail.domain.com’ could not be found. Verify that the server name is entered correctly.
POP3
The host ‘mail.domain.com’ could not be found. Verify that the server name is entered correctly.
Account: ‘mail.domain.com’, Server: ‘mail.domain.com’, Protocol: POP3, Port: 110, Secure(SSL): No, Socket Error: 11004.
Action: Check for typos in the domain name. If it’s still not working, try using the server’s IP address.
IMAP
Authentication failed. The methods supported by your IMAP server are not compatible with your computer.
POP3
Unable to log in using Secure Password Authentication.
Account: ‘mail.domain.com’, Server: ‘mail.domain.com’, Protocol: POP3,
Server Response: ‘-ERR Invalid command.’, Port: 110, Secure(SSL): No.
Action: Uncheck “Log on using Secure Password Authentication” (SPA).
IMAP
The connection to the server failed.
POP3
The connection to the server failed.
Account: ‘mail.domain.com’, Server: ‘mail.domain.com’, Protocol: POP3, Port: 1100, Secure(SSL): No, Socket Error: 10061.
Action: The incoming port is incorrect. Use Port 110 for POP3 and 143 for IMAP.
IMAP
Your server unexpectedly terminated the connection. Possible causes: server issues, network problems, or inactivity.
POP3
Your server unexpectedly terminated the connection. Account: ‘mail.domain.com’, Server: ‘mail.domain.com’, Protocol: POP3,
Port: 110, Secure(SSL): Yes.
Action: You’re using a secure connection with the wrong incoming port. Use Port 993 for IMAP and 995 for POP3.
IMAP only
The specified Root Folder ‘public_html’ could not be found or created.
Action: Leave the “Root folder path” field blank for IMAP accounts.
0x800CCC65 – This error occurs when a firewall (e.g., Zone Alarm) or antivirus software (e.g., NOD32, Norton, McAfee) blocks outgoing mail server connections. Temporarily disable these programs and check if the issue persists.
0x800CCC67 – This error is usually caused by one of the following: the ISP blocking port 25, a firewall or antivirus blocking SMTP, or incorrect Outlook account settings. Change the SMTP port to 26 and disable any security software to test the connection.
0x800CCC78 – The sender address must be a complete email address, not just a username. Update your account settings in Outlook or Outlook Express to use a full address (e.g., ).
0x800CCC79 – This error indicates that SMTP authentication must be enabled before POP authentication. Verify your email client settings and enable SMTP authentication.
0x800CCC92 – This error suggests an issue with the email account’s password or possible corruption. Log in to cPanel to verify the password or recreate the email account if necessary.
0x8004210B – This is a client-side issue. Refer to the Microsoft support documentation: https://support.microsoft.com/kb/827349.
0x8004210A – This is also a client-side issue. More details are available at https://support.microsoft.com/kb/827349.
0x800C0133 – This error indicates a corrupted Outlook Express mail store. Visit the Microsoft newsgroup for potential fixes: https://www.microsoft.com/communities/newsgroups/en-us/…. If the issue persists, consider disabling your antivirus scanner’s Outlook Express integration using the instructions here: https://www.microsoft.com/communities/newsgroups/en-us/….
0x800CCC19 – This error may be caused by local antivirus software. Refer to the Microsoft documentation for troubleshooting: https://support.microsoft.com/kb/813518.
0x800CCC0D – This error has common fixes outlined in the Microsoft support article: https://support.microsoft.com/kb/813514.
0x800CCC0E – This error occurs when the ISP blocks required email ports. More information is available in the Microsoft documentation: https://support.microsoft.com/kb/191687.
0x800CCC0F – This error can have multiple causes, including local firewalls. Check the Microsoft support article for troubleshooting steps: https://support.microsoft.com/kb/813514.
0x800CCC0B – Common fixes for this error are provided in the Microsoft documentation: http://support.microsoft.com/kb/827349.
Switch the Outgoing Port from 25 to 26, as many ISPs block Port 25 to prevent spam.
Temporarily disable antivirus or firewall software to eliminate potential interference.
If problems persist, try using your ISP’s outgoing mail server.
Verify that your internet connection is stable and working properly.
Double-check the email server settings and ensure they are correctly configured.
