MS CRM 2011 offers for options for tracking e-mail.
1. All e-mail messages
This option will track all e-mail. The major disadvantage with that is it can eliminate privacy and sometimes there are e-mails that maybe shouldn’t be tracked or that need to stay private.
2. E-mail messages in response to CRM e-mail
E-mail messages are tracked only if the person has a record in Microsoft Dynamics CRM.
3. E-mail messages from CRM Leads, Contacts, and Accounts
E-mail messages are tracked only if it comes from someone with a Microsoft Dynamics CRM lead, contact, or account record.
4. E-mail messages from Microsoft Dynamics CRM records that are e-mail enabled
E-mail messages are tracked from all record types, including custom record types, that contain an e-mail address field.