There is one big problem with email -- how do you find out someone's address ?
At present, there really isn't much of a solution as if an organisation publicises email addresses at all (and some don't -- either because it will cost someone time to do so, or in an attempt to discourage the spammers), it will probably do so in some non-standard way. Although you can try looking at an organisation's web page (if they have one), there isn't always an answer there.
There is an answer though -- directory services3.7.
In the OSI network model, X.500 provides directory services, including email addresses. Unfortunately, X.500 isn't really an Internet service, and although there are X.500 directory servers on the net, there are not that many of them. Part of the problem is that X.500 software is very complex to install, and is dependent on another piece of software that is probably even more complex to install.
An alternative known as LDAP (light-weight directory services), which was intended as a cut-down version of X.500 is available. With numerous companies and organisations flocking to the LDAP banner, it looks as though LDAP will be the service of choice for providing information such as email addresses.
Although there are LDAP servers available now, and you can certainly use them (usually through the Web), there are not enough to be certain of finding the email address you want. Just wait a few years :-)