You're okay with an executive summary at first.
But you should have a 12-15 slide deck on hand describing your business. You don't need to send the deck in initial emails (but you will send the exec summary, and others will include your summary in any email introductions), but interested investors will want the full deck to look through later.
The ideal is actually to NOT send the deck in email, and only the executive summary. The best thing is to do your pitch in person, and send the slide deck shortly before meeting. Positive decisions are more likely in person, and you don't necessarily want investors to pore over your deck before having the chance to defend it in person.
But that's the ideal. Usually you have to go with the flow, and they'll want the deck before meeting with you.
If you'd like help refining your executive summary or pitch deck, feel free to email us for feedback!