The following steps will cause all incoming email to a user to be discarded. This will not bouce message, but will prevent file space from being consumed. It also prevents any sendmail error messages being sent to CU.

  1. Create the following .procmailrc in the user's home directory 
    # Set to yes when debugging
VERBOSE=no

# Remove ## when debugging; set to no if you want minimal logging 
## LOGABSTRACT=all

# Replace $HOME/Msgs with your message directory
# Mutt and elm use $HOME/Mail # Pine uses $HOME/mail # Netscape Messenger uses $HOME/nsmail
# Some NNTP clients, such as slrn & nn, use $HOME/News 
# Mailboxes in maildir format are often put in $HOME/Maildir 
MAILDIR=$HOME/Mail # Make sure this directory exists!

# Directory for storing procmail-related files
PMDIR=$HOME/Procmail

# Put ## before LOGFILE if you want no logging (not recommended) 
#LOGFILE=$PMDIR/log 
INCLUDERC=$PMDIR/from.rc
  2. Create a Mail directory in the user's home directory
  3. Create a Procmail directory in the user's home directory
  4. Create a Procmail/from.rc file containing 
    :0:
* ^From:.* 
/dev/null
  5. Create a .forward file in the user's home directory 
    "|IFS=' ' && exec /usr/local/bin/procmail -f- || exit 75 # username"
    The last word in the line is the user's userid.
  6. Make sure all these files are owned by the user and readable, but not writable, by group and world.
Based on an idea printed here: http://www.itworld.com/nl/unix_sys_adm/12192001/pf_index.html