Actually most SMTP now talk SSL to each others, so while the hops (generally, just 2: sender and receiver) could also be compromised, the attack surface is smaller than one would think.
Not to dispute your claim, but how do you know this? Is there some sort of global, internet-wide survey of SMTP servers somewhere that supports what you say?
It's easy to tell which mail servers are using SSL by looking at your mail server logs. He probably only cares that most of the mail servers talking to him use SSL (which is also true for every mail server I have administered).
