When an incoming email or call from a non-customer begins with ""We use a really old version of MAS90"" - assume that they are not inclined to pay and have a quick summary of pricing options available to send them. Do not under any circumstances get on the phone listening to their various problems which will all end with you being queried for a ""quick question"" (aka no cost) answer to their ""easy"" question.
Believe me - just throw these back because you're never going to bill anywhere near the value you provide.