Return receipt?

Hi,

My boss uses Pegasus, and sent mail with "Return receipt" on. 
I was surprised to read the following on his machine: (edited)

Subject: Returned mail: Return receipt

  The original message was received at Wed, 1 Nov 1995 11:25:00 -0600
  from eniac.ac.siue.edu [146.163.15.8]
  
     ----- Transcript of session follows -----
  procmail: [6456] Wed Nov  1 11:25:00 1995
  procmail: Assigning "PATH=/home/labash/bin:/usr/bin:/bin:/usr/local/bin:"
  procmail: Assigning "MAILDIR=/home/labash/Mail"
  procmail: Assigning "DEFAULT=/home/labash/Mail/mbox"
  procmail: Assigning "LOGFILE=/home/labash/Mail/from"
  procmail: Opening "/home/labash/Mail/from"
  <labash(_at_)lcjones(_dot_)aclib(_dot_)siue(_dot_)edu>... Successfully 
delivered
  
     ----- Message header follows -----

Have I misconfigured something?  Is there some way to stop this information
from being visible to the outside world?

Thanks.
-- 
Louis-ljl-{LLaBash(_at_)eniac(_dot_)ac(_dot_)siue(_dot_)edu | 
lou(_at_)minuet(_dot_)siue(_dot_)edu}