🚀 go-pugleaf

Every once in a while, when responding to a message on this service, I get it
returned as undeliverable. This is probably a stupid question, but can
someone please tell me how to overcome this problem?

(Example of returned message follows) 
From wnn Wed May  3 13:36:07 1989
Date: Wed, 3 May 89 13:34:13 EDT
From: MAILER-DAEMON (Mail Delivery Subsystem)
Subject: Returned mail: Host unknown
To: wnn
Status: RO

   ----- Transcript of session follows -----
550 charis.chem.rpi.edu.tcp... 550 Host unknown
550 jtwarden@charis.chem.rpi.edu... Host unknown

   ----- Unsent message follows -----
Received: by dsunx1.DSRD.ORNL.GOV (5.57/Ultrix2.4-C)
	id AA09401; Wed, 3 May 89 13:34:13 EDT
Date: Wed, 3 May 89 13:34:13 EDT
From: wnn (W. N. Naegeli)
To: jtwarden@charis.chem.rpi.edu
Subject: PhoneNet stars

I am interested in getting more details about your dual star network, you
mentioned on info-appletalk.
How far are the stars apart?  Directly linked or through a bridge?
Are these passive stars or are you using a StarController?
How long are the spokes?  Where are the terminating resistors?
Where is the FastPath?
Any problems with certain nodes not seeing other nodes?
   We have a multi-star network and some problems. We have tried the Tops
Repeater and the TurboBridge, but they seem to make things worse rather than
better. Your information would help us better understand what works and what
doesn't.  Thank you.

Wolfgang N. Naegeli
Oak Ridge National Laboratory
wnn@dsunx1.dsrd.ornl.gov (128.219.96.46)
(615) 574-6143

(end of retruned message)

Any help with this case and in general would be most appreciated.