Could somebody help me understand how to set up the parser email? 

We have built a simple email template which each sales person can send to their client requesting information from the client to ensure we have the correct invoice details stored so we can send the customer a correct invoice. Some of these fields can by auto populated from fields in the CRM. The template requests that the customer fills in the missing data eg additional names to appear on the invoice etc. prior to returning it to us. When the customer completes this template can the returned email be parsed into the CRM. If so, how is this achieved?