If you are one of the first 16 mails with a VALID giveaway code i receive, i'll put the sha256 hash of your giveaway code next to your slot (0-f) and announce a future block whose hash's last character is used to announce the winner.
Once the giveaway is finished the winner has 48 hours to send a mail to mocagiveaway@gmx.com including his/her physical address (signed with the address in their original email) (including a phone number, so basically: your name, your street + number, your zipcode, your country, your phonenumber).
And you didn't provide a list of people who emailed you, how do they know if they're one of the first 16 Once the giveaway is finished the winner has 48 hours to send a mail to mocagiveaway@gmx.com including his/her physical address (signed with the address in their original email) (including a phone number, so basically: your name, your street + number, your zipcode, your country, your phonenumber).
How do they know who are the winner if they don't know what their sha256 hash is 
Wish you success in trying out new features
Everything will go smoothly!