Hi Mahathi,
Unlikely to be a robotframework library for this as it's not something people would do often.
One of the really powerful features of robotframework is the ability to create your own keywords that are actually python functions, so you can use any python library in your custom keyword that does what ever you want it to.
Using that info I would suggest creating 2 keywords:
1) "open pst file" - pass this keyword the pst file you want to open, returns a pst object
2) "get email accounts" - pass this the pst object, and it should return a list or dictionary of the email accounts
From there you can use standard robotframework keywords to do what you need with the account information.
Also if you need to retrieve other information from the pst file, you already have the keyword to open the file, so it should be easy enough to create additional keywords for different actions.
Hope this helps you get started and good luck,
Dave.