Well, the choices are:
1 - Display server messages as is
2 - Mangle them into some sort of condescending baby talk:
"Your mail server doesn't seem happy, it said, I'm sorry, Dave, I'm afraid I can't do that."
3 - Neither fish nor fowl, and combining the disadvantages of both.
Personally, I hate the second option.
To someone knowledgeable, it hides information that may be useful.
To someone who's not, it's meaningless gibberish either way, so no gain.
It makes providing support more difficult.
And it makes it pretty much impossible to "Google" (or "Bing" or "Yahoo") the error message.
Bottom line -- I think that verbatim error messages are a thousand times better than "baby talk" in terms of helping the user (and me) solve whatever problems may come up.