As I figured.
Here was my official reply I sent to him:
"RFC-2822 is a Proposed Standard according to the Official Internet Protocol
Standards. We are completely compliant with RFC822, which is the current
standard for MAIL. If your software in unable to handle older standards, it
is suggested that you upgrade.
In regards to what mail platform we are using, we do run Microsoft Exchange
5.5. If you would like us to upgrade, I can forward you bank details so you
can wire us $45,000 - the cost of switching to another product. Until then,
please discontinue these unsolicited memos, for the public good."