Finding people on the network

[Raymond Yee]

I don't know whether this is the appropriate group, but I'd appreciate
answers to the following questions:

1) Is there a way to find the email address of a person on a network
if you know his name and organization (eg, university)?  I know that
finger will work if you have the host also.

2) Is there a way to get the list of all the login names on a given host.
I know that one machine I have access to, there is the command:
     finger -a
On other machines, there is no corresponding option.

3) Which users do the whois command bring up?  How do they register to
be in that listing?

Thank you in advance,

Raymond Yee