Error code 0x800CCC0F is generated when sending mail from Microsoft Outlook


Error code 0x800CCC0F is generated when sending mail from Microsoft Outlook


This error is generated because the mail client (Outlook) is unable to contact the MailEnable server.  The most likely reason is because a firewall is preventing connectivity between the client and the server.


As a preliminary measure, review the Diagnostic Report to ensure that the services (POP, SMTP, etc) are configured and are running on the MailEnable server. If the services are not running, start them and subsequently re-attempt connecting from the mail client.

Diagnosing this issue involves troubleshooting the network environment to determine what is preventing Outlook from connecting to the MailEnable server. This can initially be done by first using the ping utility to see if the DNS is able to resolve the specified mail server name to an actual IP address.

STEP 1: Check that your DNS resolution is working correctly

From the Windows command prompt, please type this:

ping [name/IP of mail server as specified in Outlook settings]

e.g.  ping

A reply response indicating the IP address of the server should be returned. 

If an IP address is not reported when the ping is being performed, then review the DNS configuration.

NOTE: The NSLOOKUP utility can also be used to check DNS configuration/integrity. For details on using this utility, please see

STEP 2: Check TCP/IP-Network Connectivity

Assuming that the ping returns an IP address in its response (even if it returns an error in being able to get the response itself), then the next step is to determine if the mail client is able to connect to the ports on the MailEnable server. This is done via the telnet utility.

From the mail client's Windows command prompt, please type in the following:

TELNET [name/IP of mail server as specified in Outlook settings] 25

eg: Telnet 25

It should connect to the server and report back with a welcome note from the MailEnable server.

If nothing (or an error) is returned, then something (most likely a firewall) is blocking connectivity between the mail client and the server. In this case, check with your ISP to see if they allow connection to external mail servers.  Check the logs of any firewalls that are installed.


Diagnosing Outlook/Outlook Express Error Codes:

Product:MailEnable (All Versions)
Class:ERR: Product Error
Revised:Wednesday, May 4, 2016