no reply if host down

Dear Clement,

I hope you're well. After quite a while, I have a question again:
It appears to me that if the target host in my request is down, as it is
the case with www.w-box.de, www4mail sends no reply at all back to me.
Moreover, such a request doesn't even affect my quota - a request for
another site sent after the one to www.w-box.de showed a quota count one
less than before. Perhaps the response from www.w-box.de is still waited
for by www4mail - forever queued?
Could this be so? That would not be an ideal behaviour, for one could be
tempted to send a request again and again (as I have been).

Best regards,
Dietmar