With Sme as with most Apache web servers webmail is an alias
You can modify the http.conf to point it to wherever you want
Sme has used templates to do this so they need to be changed instead of the direct http.conf like all other systems
edit the /etc/e-smith/templates or the /etc/e-smith/templates-custom to do this
look for the http.conf and change the alias to webmail
it is the same for using apache's http.conf
alias billybob /my/webmail/directory
get it?
now billybob points to your webmail directory
hope this helps