Save it as a text-only file in a word processor. Separate the interview into smaller sections. Email it in parts. You then can email an ongoing, valuable document that includes advertising, rather than another sales letter. Create several follow-up letters.
First contact is a free report or newsletter.
Second contact means checking in to see if they have any questions, and making them a special offer. Third contact should qualify them to see if they want to explore working with you. Don't give up with one or two messages unless they ask you to. Set up interviews. The real goal is to get them to respond to your message.