I've just started to notice these unusual bounces from
CI$:

From: Mail Delivery Subsystem <[log in to unmask]>
Subject: Returned mail: Service unavailable
Message-Id: <[log in to unmask]>
To: <[log in to unmask]>

The original message was received at Thu, 13 Feb 1997 12:57:00 -0500
from psuvm.psu.edu [128.118.56.2]

   ----- The following addresses had delivery problems -----
<[log in to unmask]>  (unrecoverable error)
<[log in to unmask]>  (unrecoverable error)

   ----- Transcript of session follows -----
554 <[log in to unmask]>,<[log in to unmask]>... Service unavailable

------

I suspect that you'll see them too.

/Pete Weiss at Penn State