Key components of the final email:
1) Make sure that in the subject heading, it clearly states that this is your final attempt to get sponsorship for your Campaign. Something like "Last chance to support my Campaign".
2) In the first two or three sentences, make a final request for donations, including a link to your Campaign page.
3) Thank those who have supported you.
4) Let people know how the campaign experience was: what you accomplished, how it felt, how it felt to raise money and to get the support of your community, etc.