You can always send mails using other MTA, as long as your mailhost entry is right in your sendmail.cf
Here is an example:
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
# "Smart" relay host (may be null)
DSmailhost$?m.$m$.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Replace mailhost with your MTA name.
Or there is another quick and temporary solution. You could send you local domain mails like this:
echo "test mail body" | mail -s "mail subject"
rakesh.malik@mymta.mydomain.com
This will forward the mail to mymta.mydomain.com and you MTA will decide where to send the mail.
Hope this will help!