In this article, we discuss how to write a business proposal letter and we offer sample letters and templates you can use as a guide. We've rounded up 4 unique methods for writing proposal submission emails.Plus, we've got email samples for each method. This proposal email template is designed for impressing clients with your achievements, social proof, or positive testimonials. We'll show you an example of a followup email to send a client after sending a proposal so you actually get a response! A business proposal email is a persuasive sales document sent to clients to gain business. Learning how to write an effective business proposal is essential. Step 1: Fill out the form. Learn how to craft an effective business proposal email with our comprehensive guide. I remember my first proposal.