Retrieving contact from yahoo, gmail, msn, hotmail, aol, etc

This is a dangerous practice since you are essentially giving away your yahoo/gmail/hotmail/aol ID and password to a third party.

Don't hold any illusions that it's some kind of 'pass-through' technology or that your account information isn't really stored anywhere.  You gave away your password and you have to trust that third party to not act maliciously.

This is like when people use the same username/password for Yahoo and Hotmail.  You are essentially giving your Hotmail credentials to Yahoo employees.  While it's a very bad thing to do, the fact is that lots of people use the same password everywhere.

In theory, I could create a system that leeches off Yahoo's authentication.  For example, I'd setup foobar.com with a login screen and tell users to enter their Yahoo ID & password.  Once they submit the form, my server attempts to log in to Yahoo using their credentials.  If it works, they are granted access to foobar.com.  If it fails, they are denied.  This saves me the trouble to creating my own signup system and means that my users don't have to remember yet another password.  When people do this maliciously, it's called 'phishing'.

Don't do it!  For a better 'single-login' system, check into the OpenID initiative:
http://openid.net/

That is why Im planning to have both... as an option for user to pick whether or not to use and pratice this pass-through technology or to use the traditional manual method...

Still hoping for an answer to the pass-through method though... and thank for reply too william...

Can you restate your question?  The only thing you asked was if anyone was familiar with the technology.  Where you just curious how they did it or were you looking for an algorithm to parse an address book from Yahoo?  or Hotmail?

Roughly they use an application on the server to apply your login credentials to yahoo.com.  For example, it's not difficult to use PHP to submit a form to another server, capture the output, and parse it.

Ok.. basically I need the script which is capable of doing what I meantioned earlier which is to allow user to enter their ID and password and with that am able to retrieve contact or address book from that particular given account provided the login information given is the correct set.

In brief the working script should be able to:
- Authenticate yahoo/gmail/aol/hotmail ID and Password provided
- Retrieve the contact list or address book once authenticated into a list of notepad or list those contact directly on webpage
- Password preferred to be encrypted

Tutorial on Page Scraping
http://www.dmxzone.com/ShowDetail.asp?NewsId=4402