Get contact list from gmail, yahoo, hotmail

I wish to write an API that can get the contacts list from Gmail, Yahoo and other e-mails. How can this be done? Are there already existing APIs for them or do I need to write PHP code to extract information?

I need a referral system like DropBox has. Has anyone coded it themselves or is it available as open source?

https://www.dropbox.com/referrals

Please guide me in this regard. Any link 开发者_开发百科or explanation will do the job.

Thanks :)

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Google has an API: http://code.google.com/intl/en/apis/contacts/ And Yahoo also has an API: http://developer.yahoo.com/social/contacts/

There exists some other which are mentioned in this thread: PHP APIs for Hotmail, Gmail and Yahoo?

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simple 5 step to get contact list from gmail 1. open gmail account 2. click gmail dropdown 3. click on Contacts 4. Click on More dropdown button 5. Now click on Export... , and download email db

http://all-easy-tricks.blogspot.in/p/how-to-get-gmailemail-id-contacts-list.html

click here