If you simply forward an email you have received in your inbox into your CRM account email drop box address it will associate the email with your own contact record and not the actual persons record who sent you the email.
This is because you are forwarding from your email address into your email drop box address - so it links to your own contact record only.
If you want to forward an email you have received into your CRM account - into the actual contacts record where the email is stored inside the contacts history you must follow the instructions contained in this link.
If you just forward the email into your email drop box address - the email will associate with your own contact record and not the actual persons record you want to store the record of the email inside of.