I had him take protocol trace (a luxury that one does not often
have with customers) and he sent it to me. It turned out that the other
product was incapable of dealing with Telnet option requests coming from
the client. I reported this to him, noting that it was a truly creative
deficiency on the part of the other vendor, and a massively profound
deficiency, at that.
He said fine, and then asked me what I was going to do to fix our
I sputtered and repeated that it wasn't our bug and that he needed
to get the other vendor to fix THEIR friggin' product.
He said he understood that, but that we were much more responsive
to fixing problems.
I've been in this position so many times, I've lost track. And to be fair,
X.400 has proved to be an especially fertile ground for these sorts of
"backwards solutions" -- much more so than Internet protocols have.