Possibly it was a good thing for the irritating salesperson to see this?
I immediately wrote to salesperson:
I stand by this even as I intended to write to [colleague]and not you.
I am feeling a little overwhelmed by the emails and phone calls and texts right now as I focus my attention on fully evaluating EDMS systems. I am the lead on the project, and it was unnecessary for you to contact [colleague] when I didn’t return your voicemail as quickly as you wanted (I was in the middle of a session when you called).
I have a minefield to work through at work with senior management, and [colleague] is not the right conduit for communication with senior management, I can assure you.
However, I'm sorry you saw my grumpy email.
He wrote back extremely apologetic and we've worked it out. But whoooo boy what a little panic I had. Until I realized he's the salesperson, not me. He's the one who should worry. That it made it easier to deal with.