Dear Ms. Christian Emerson,
It is a privilege to connect with you and writing to you in person. I am part of ---- (workplace/university) and have been associated with it over ----- (mention the time). Now, I/We are looking forward to organizing/starting ---- (the reason for sponsorship) and are looking forward to your association with it as a respected sponsor.
The ------ (objective) is to help the society as a whole and would like to work towards its benefit. The ---- (event/course) is beneficial for both parties as it not only boosts the presence in the society but also brings the change in making your organization look like a respectable one in the society.
I hope after going through this mail and knowing about the subject of the sponsorship, you will more than eager and glad to be associated with it and take this forward as a prosperous association. I have also added my contact details in the letter and would request you to let us know how to get in touch with you.
If you have any doubts about the ---- (mention the reason) please feel free to call me and discuss it in detail. Once you are convinced, then we can also arrange a meeting and take this forward to finalize the association.
Thanking you for your time and support and I will be looking forward to hearing a positive response from you.