It's easy to add your signature to e-mails, but what if you use different signatures for different types of e-mails? For example, you may have different signatures for internal and external communications. You can make one signature your default signature (pick whichever signature you use more often)...

Source: http://www-10.lotus.com/ldd/notestipsblog.nsf/dx/using-multiple-signatures-in-mail