Finally got it working, so if anyone else is trying to do the same thing this is what you have to do:
Add the following to your mc file used to generate sendmail.cf:
FEATURE(`genericstable', `dbm /etc/mail/genericstable')dnl
Of course you can change the names of the files to be what you want. These are only suggestions.
use the m4 command to do this. While in /usr/samples/tcpip/sendmail.cf run the command:
m4 ../m4/cf.m4 your.mc > /tmp/sendmail.cf
vi /etc/mail/genericstable. Add the users you want to change the email address for. The format is 'user firstname.lastname@example.org
'. The file is tab delimited.
After you have made the file use the makemap command to get it ready for sendmail to use. 'makemap dbm genericstable < genericstable'
Run the following command as root:
sendmail -bt -d0.1 < /dev/null
This will give you an idea of what you need to place in the genericsdomain file. This does not need to have anything done to it, so just leave the file as it is.
Move sendmail.cf into place
Now that everything else is done, move /tmp/sendmail.cf to /etc/mail. Restart sendmail if it is actively running on the system.