Outlook Error 0x800ccc0f Outlook (or Outlook Express) reports the following error when trying to send mail: 0x800ccc0f when attempting to send an email. If this issue only occurs with a select few clients it is likely that the DHAP feature of MailSite is blocking them. See KB article 10280 for details on how to remove specific IP addresses from the DHAP probation list. MailSite 7.0.3 and later provides the ability to whitelist IP address from the DHAP feature. Once you have corrected the problem, you may need to restart Outlook (or which ever email client you are using).