When you use Outlook, Windows Live Mail, Windows Mail, or Outlook Express normally, you may rarely encounter problem like 0X800CCC0F, it may be –
- network connection problem (visit some website to test it), or
- the connection interrupted by anti-virus software (check your desktop antivirus log), or
- the connection interrupted by a network firewall (check your desktop/network firewall log), or
- the connection interrupted by other firewall on Internet
Also, you may consider to login to webmail to check recent mails, especially those emails near the time of the problem.
After reading it at webmail, delete it (and empty the trash), and try again inside Outlook.
Other details can refer to –
https://support.microsoft.com/en-hk/help/813514/error-occurs-when-you-send-or-receive-an-email-message-in-outlook-or-o
