Yeah I advise early stage startups and they are either way too formal, or completely lacking in the basic understanding of how to communicate professionally.

Like it's either

"Dear Sir, I am writing to acknowledge that you RSVP'ed yes to our calendar invitation" or

"sorry about missing the meeting. we didn't end up making a power point, so we'll just send you a couple drawings our friend did of a different thing that's pretty close to what we were thinking of doing."