# cd /usr/share/sendmail/cf 

make a backup
# cp openbsd-localhost.mc openbsd-localhost.mc.example

edit config, adding the following lines *IN THE APPROPRIATE SECTIONS* of the conf
# vi openbsd-localhost.mc

	FEATURE(masquerade_envelope)dnl
	FEATURE(`always_add_domain')dnl
	FEATURE(`genericstable',`hash /etc/mail/genericstable.db')dnl

	GENERICS_DOMAIN(`yourdomain.com')
	
	define(`SMART_HOST',`mail.verizon.net')dnl

run m4 to output the conf file we're actually going to use 
# m4 ../m4/cf.m4 openbsd-localhost.mc > /etc/mail/localhost.cf

map outgoing (from) addresses from local machine accounts to whatever you like 
# vi /etc/mail/genericstable 

	root <TAB> you@your_other_domain.com
	root@host.example <TAB> you@your_other_domain.com

hash the table into usability
# makemap hash /etc/mail/genericstable.db < /etc/mail/genericstable

find the running sendmail process
# ps ax | grep sendmail

restart it to update changes
# kill -HUP <sendmail pid>