The typical and professional way of communicating with investors and capitalists is via email. Drafting an email to the investor is more of an art and skill, and it should be crisp and to the point.
Here are the breakups of what and how your email should get structured:
You as an entrepreneur have to draft a compelling subject line. It will grab attention and make a soothing psychological effect if your subject line is to the point. The subject line also needs to show that you understand what you are doing and even your investor. It should not look like spam. For drafting a subject line, you might have to research the investors.
The Body of Email
When the investor opens your email, it should also be precise. Less is more when it comes to the body of the email. It may comprise of 5 to 6 lines at max which may include who you are, what you want, what you do, how can we proceed - i.e., the business model and about your idea or product. Imagine every investor is receiving 100 to 200 emails per day, so write the lines as accurate as possible, and cut to the point. The body of the email is the micro-chasm or smaller version of your pitch.
Do not put any large attachment. Let suppose you send a 30 to 40 MB of PowerPoint presentation; you are done because that investor sees the size of your enclosure won't open that at any cost. So, make sure file size is 2- to 5 MB at max.
Done, you're good to go with your idea. Send the email and politely reply to investors and try to understand what and how they want things to be done.