Right-click the SMTP virtual server, and then click
On the Access tab, under Access control, click
In Authentication, select Basic
Select the Require TLS encryption check box.
In Default domain, type the Windows domain which, by
default, will be used to authenticate users.
Note Users outside the
default domain will also be able to authenticate, provided an
Active Directory trust relationship exists between their domain and
the default domain. Users outside the default domain will have to
specify the domain authorized to validate their
To return to the Access tab, click OK.
Under Secure communication, click
In Security, select the Require secure channel