...that a message can move from my Outbox to my 'Sent Items' folder without the other person having read it??? I won't name names, but I am having sort of a 'red flag' moment here on a sale I'm trying to negotiate...
Not that I am aware of. But also keep in mind, that people browse email and respond at a later time. I know that I have done that.
One thing to remember is that everyone is different with sales. Sometimes people don't go by the "FIRST to PM" stuff and just because you messaged someone means that they will always respond.