If you are actually sending content (video, white paper, eBook, comic, etc.), then I agree with Grant. No one likes long emails or large3 attachements. There are, of course, cases where you will want everything contained in the email itself, such as templated intro messages, meeting follow-up messages, etc. In those cases, I feel that it is often better to include a link to a presentation or a meeting recap, etc.
Landing page. We have a landing page type we create regularly for the sales team called 'prospect landing pages'. We have an easy template ready to go, they send us the content and a short message they want to provide to the prospect and we populate the page and have a nice easy URL for them to share.