hostname = mail.srever.com
ip= 128.10.35.1
ip range 128.10.0.0-128.10.255.255
change yor ip n all other according to yor requiremnt...im writin all this..in order to give u a idea
i hope evry1 here musy be knowing what dhcp is.
# service dhcpd status
# service dhcps start
if it was allready started then
#service dhcpd restart