Hi,
It sounds like you are using the Outlook client to track your emails to CRM so you must use Outlook to track emails. See this page for different ways of tracking email
https://technet.microsoft.com/en-us/library/dn832099.aspx?f=255&MSPPError=-2147217396
Also, you must ensure that email addresses involved in your email recipients exist in your CRM on contact/Account or Lead records (or email enabled custom entities)
You can view emails that exist (are tracked) inside crm via the 'Activities' tile in crm. you can also use advanced find and look at the email message entity.
Rob
MCTS. GAP Consulting Ltd. Microsoft Community Contributor Award 2011 & 2013