.local and .com?

i installed server 2003 on a virtual machine and
made the 1st domain home.local. then i
installed exchange server 2003 succesfully
and gave my users mail boxes. when i started
outlook as the users i realized their email was
XXXX@home.local.
how do i keep the .local domain. and add a
new .com domain for emails on the same
server? or is it too late? thank you