Every email sent uses directories. Lotus Notes uses at least one directory, and often several. The directory is more than just a list of names; it can provide information and act as a service. Some of the information is obvious: names, addresses, and phone numbers. Complex directory services can include automatic look-up and referrals, and can act as a binding agent for authentication.
Here is one example of how directories simplify your life. Let's say you need to send an email to your friend Mike. Mike's email database is located at:
To send a message, you would need to create an address: something like