(non)delivered messages - Inbound/Outbound mail failure

[piti]

When replying to some mails, administrator gets 2 messages as follows:
***************
subject: "Notification: Inbound Mail Failure"
body: The following recipients did not receive the attached mail. Reasons are listed with each recipient:

<ZiskM@ba.spas.sk> ZiskM@ba.spas.sk
MSEXCH:IMS:*****:SERVER:**** 3554 (000B099C) 554 buildaddr: no host

The message that caused this notification was:
attachment: the replyed message without text in the body(only header)
**************
subject: &quot;Notification: Outbound Mail Failure - A protocol error occurred.&quot;
body: A mail message was not sent due to a protocol error.

554 buildaddr: no host
The message that caused this notification was:


To: <ZiskM@ba.spas.sk>
From: <>
Subject: Delivered: RE: po vikende
******************

But the message is delivered. Is there any missconfiguration on the exchange server or what?
Anyone knows how to solve this &quot;problem&quot;?
thanks