OUTLOOK SENDING RECEIVE ERROR 0x800ccc0f: 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.

This error can arise without warning or any prior symptoms and hence can be very startling. To resolve it, you need to find the exact cause behind it and eliminate it completely.

Common reasons behind error 0x800ccc0f include:

• Slow Internet connection or connectivity issues with the Exchange server
• Firewall blocking MS Outlook outgoing and incoming messages
• Incorrect Outlook profile settings or corrupted Outlook profile
• Technical issue with the server settings
• OST file corruption

1. Check for connectivity issues

The first step should be to check is your machine’s connection with the Exchange server. For this check both the Internet connection as well as the access gateway connection to the Exchange server. Make sure the configuration and settings are correct and that everything is in place.

2. Disable anti-virus and Windows firewall

In addition to Windows Firewall, your anti-virus program might also hamper the smooth working of incoming and outgoing emails. Thus, to check if this is the issue, disable your anti-virus. Also disable Windows Firewall as follows:

Open Control Panel and go to Network Connections
Right click on the internet connection you’re using and select ‘Properties’ from the pop-up menu
Under the ‘Security’ tab, switch off the Firewall

3. Check Outlook profile settings

Check your default Outlook profile’s settings. If they are incorrect, correct them. If you’re not sure about what is wrong, delete the current default profile and create a new one. Then set the newly created Outlook profile as the default profile.

4. Clear up suspicious emails from Outlook and Outlook Outbox

Sometimes, suspicious emails or emails with un-trusted attachments might be the real reason behind this error. If you think there are such emails within your Outlook inbox, delete them immediately. Also, if your Outlook outbox is overcrowded, clear it up (only the Outbox).

5. Verify your router’s MTU

The Maximum Transmission Unit (MTU) size of your router might also be creating this issue while sending / receiving particular mails. Check it and make changes to outgoing message sizes accordingly.