[CentOS] dumb sendmail question -- how to get outbound messages to use "example.com" instead of hostname?

     On our servers here are some sendmail.mc lines referring to our domain.
 May be they will help.  These are from our main server:

define(`confDOMAIN_NAME',vigyan.com)dnl
CLIENT_OPTIONS(`Family=inet,Addr=vigyan.com')dnl
define(`SMART_HOST',`vigyan.com')dnl
FEATURE(`smart_host_domain',`vigyan.com ')dnl

These are from our slave servers:

CLIENT_OPTIONS(`Family=inet,Addr=slave.vigyan.com')dnl
MASQUERADE_AS(vigyan.com)dnl
MASQUERADE_DOMAIN(vigyan.com)dnl
FEATURE(`allmasquerade')dnl
FEATURE(`masquerade_entire_domain')dnl
FEATURE(`masquerade_envelope')dnl
define(`SMART_HOST',`slave.vigyan.com')dnl
FEATURE(`smart_host_domain',`vigyan.com ')dnl

     Good luck.