There is no sure way to do it, but you can try.

Many of the services below are being restricted to protect the provace of
the people involved, as well as because of computer crackers...

1) Call the person or the secretary and ask. It is amazing how many people
   forget about this option.

2) Checking the address if you know the tcp address of the machine. For
   example, you want to check if mail address name@machine.addr is fine:
     telnet machine.addr 25
     vrfy name
     quit
   If vrfy responds with
    250 
   The address in known to the machine

   Sometime, the machine.addr is not a full address but only an MX record.
   you can get the full address by saving the following script in hostlook
        #!/bin/sh
        # this file is called hostlook        
        MXREC=`nslookup <<_END_ | tail -2
        set qt=MX
        $1
        _END_`
        echo $MXREC
   with execute permission (e.g., chmod 755 hostlook), and calling it as 
        hostlook ccl.net.
   Note the period "." at the end of the machine name. It has to be there.

3) Use finger (though it only works with a few machines). E.g.:
     finger jkl@hawkeye.ccl.net

4) Use gopher. Frequently the organizations provide WHOIS database on
   gopher which you can search by name. Go to All Gophers, then continent,
   then country, then organization. If you know, the address of the
   whois database, you can submit queries directly
      whois -h osu.edu labanowski
   If you do not have the whois program, you can still try telned to
   port 43:
      telnet osu.edu 43
   The list of available whois servers can be retrieved from the anonymous
   FTP/mail-server rtfm.mit.edu in the directory pub/whois or via gopher
   sipb.mit.edu You may also find a list of people who recently
   posted something to the Usenet newsgroups in directory
   pub/usenet-addresses/lists} of anon. ftp rtfm.mit.edu.


5) There is also X.500 finder on gopher in Europe. You can also do it by 
       telnet hypatia.umdc.umu.se 23
       login: de
   Then follow instructions (one entry per prompt). For example:
        Simple query mode selected
        Person's name
        :- Schultze
        Department name, * to list depts,  to search all depts, ? for help
        :- 
        Organisation name, 
        :- kiel
        Country name
        :- de
        Germany
                             
        Got the following matches.  Please select one from the list
        by typing the number corresponding to the entry you want.
 
        Germany
         1 Fachhochschule Kiel
         2 Universitaet Kiel
        Organisation name,
        :- 2
        Germany
         Universitaet Kiel
         No persons match `Schultze'.        Displaying organisation details.
 
         Germany
         Universitaet Kiel
         postalAddress         Universitaet Kiel 
                              Ohlshausenstr. 40-60 
    Exit by typing q
         :- q
  

6) Use netfind (if you can get to it, it is very busy).

        archie.au (AARNet, Melbourne, Australia)
        bruno.cs.colorado.edu (University of Colorado, Boulder)
        dino.conicit.ve (Nat. Council for Techn. & Scien. Research, Venezuela)
        ds.internic.net (InterNIC Directory and DB Services, S. Plainfield, NJ)
        eis.calstate.edu (California State University, Fullerton, CA)
        hto-e.usc.edu (University of Southern California, Los Angeles)
        krnic.net (Korea Network Information Center, Taejon, Korea)
        lincoln.technet.sg (Technet Unit, Singapore)
        malloco.ing.puc.cl (Catholic University of Chile, Santiago)
        monolith.cc.ic.ac.uk (Imperial College, London, England)
        mudhoney.micro.umn.edu (University of Minnesota, Minneapolis)
        netfind.anu.edu.au (Australian National University, Canberra)
        netfind.ee.mcgill.ca (McGill University, Montreal, Quebec, Canada)
        netfind.if.usp.br (University of Sao Paulo, Sao Paulo, Brazil)
        netfind.oc.com (OpenConnect Systems, Dallas, Texas)
        netfind.sjsu.edu (San Jose State University, San Jose, California)
        netfind.vslib.cz (Liberec University of Technology, Czech Republic)
        nic.uakom.sk (Academy of Sciences, Banska Bystrica, Slovakia)
        redmont.cis.uab.edu (University of Alabama at Birmingham)

   telnet bruno.cs.colorado.edu (or redmont.cis.uab.edu or ds.internic.net or
                                 mudhoney.micro.umn.edu or hto-e.usc.edu or
                                 netfind.sjsu.edu)
   login: netfind
     search
       labanowski osc
         --- then enter selection and wait for answer.


7) Use NIC WHOIS  (mostly military people)
   telnet nic.ddn.mil
   whois
   smith, john
   quit
   exit


8) Retrieve files from the directory /pub/chemistry/info/e-mail-addresses
   a) Via e-mail:
     send a message:
        select chemistry
        size 60kB
        limit 250kB
        cd info/e-mail-addresses
        get college-email.faq.1 college-email.faq.2 college-email.faq.3
        get finding.addresses.faq
        quit
   to MAILSERV@ccl.net

   b) Via ftp
     ftp ftp.ccl.edu
     Login: anonymous
     Name: Your email address
     ftp> cd pub/chemistry/info/e-mail-addresses
     ftp> mget college-email.faq.*
     ftp> get finding.addresses.faq
     ftp> quit

   c) gopher
     gopher gopher.ccl.net
       info
         e-mail-addresses


Jan Labanowski
jkl@ccl.net