Here are ten suggestions from the Bloomerang blog, compliments of Future Fundraising

Man_Reading_Digital_Newsletter_tcm21-54327.jpg1. Subject line. Remember what it’s for: To get people to open the email.
2. Clean images with small file sizes.
3. Personalized greeting. Use the recipient’s name. Unless you know things are likely to go awry.
4. Donor-centric tone. Make it about them, not you.
5. Specific appeal. As them to do one specific thing.
6. Suggest donation amounts.
7. Communicate impact. Show them they can make a difference.
8. Short — get them to your website.
9. Personalized signature.
10. Style and grammar rules don’t apply. Warmth, urgency, and connection do.

Source: http://tinyurl.com/kejsrmc
Original article: https://bloomerang.co/blog/10-steps-to-a-successful-fundraising-appeal-email/