Greetings bhanuk and welcome to groovyPost!
First, it's important to understand the recovery of email while using Microsoft Outlook and Microsoft Exchange is possible because it's a feature of Microsoft Exchange IE: you can configure Exchange to retain deleted email in it's database for X days after it's been deleted from a mailbox.
Other systems like PostFix will need to have a similar feature in order to recover email from the server after it's been purged from both the Outlook Client and the Email Server.
It's also important to understand POP vs. iMAP. Typically when you connect to an email server using POP, the email is downloaded to the email client but the email remains on the email server. You can configure on the client how/when/if the email is purged on the email POP server. IMAP however is much more of a real-time sync. If you delete the email from the client, the server instantly deletes it as well.
So, with that said my first question is - what are you using? POP or IMAP to pull down the email? If you want to recover the email, hopefully your using POP and the email is still on the server.
If the email is gone off the server, then hopefully the email server has a recovery feature similar to Microsoft Exchange (however that's probably unlikely). As you can tell from most of my Articles, most of my experience is with Microsoft software so don't take my word for it. Several others who frequent the forums here will probably be able to confirm that.
So if the email is gone off the server and outlook, then your only chance is that you can recover the email from the .PST file that your Outlook client users to store the email. Outlook stores email in a database so even after you delete the email, it actually doesn't purge it from the database. This is true unless you use the "compress" feature in outlook. That will nuke all old email as it compresses the database and "defrags" it so to speak...
More information on the topics here: microsoft-office/email-dissapeared-from-my-outlook-client-how-can-i-undelete-it-t95611.html
So to pull the email from your .PST file all you need to do is try a GOOGLE search for an EMAIL RECOVERY tool which can pull email from a .PST file (sometimes called an Outlook Archive file). OR, you can just use the FREE method but corrupting the .PST file yourself with a HEX editor (notepad++ etc..) then use SCANPST.EXE to repair the file
which essentially restores all the email in the database.
Keep us updated!