procmail & .forward

[NSL sysadms <jeetu cse iitb ac in>]

can you please tell me what is the significance of the following line in 
.forward


"|IFS=' '&&exec /usr/bin/procmail -f- ||exit 75 # username"


i am getting an error

   ----- The following addresses had permanent fatal errors -----
"|IFS=' '&&exec /usr/bin/procmail -f- ||exit 75"
    (reason: Service unavailable)
    (expanded from: <username my-server com>)