Emails sent to contacts via email clients such as Outlook, Gmail, iMail etc will be shown as 'Email' inside your contact's history as shown below:  


But they will not show a message status such as 'SENT', 'OPENED' or 'CLICKED' etc as they are sent via your email client (with a copy stored inside the CRM account) as shown above.

Email sent out via the the CRM e-Marketing service are sent out over the e-Marketing platform and so is a different route to those emails sent from your email client and therefore you will see a mail status such as 'SENT' alongside any emails sent out via the e-Marketing service as shown in the example below: