How to Login automatically in a BSP application from email

Hi Every1,

i m working on ESS portal for Leave Processing module.

What i m doing is when a user apply for a leave an e-mail is sent to his supervisor which contains a link Process Leave Request.

what i want is when the supervisor click on this link

he should be automatically login in ESS portal and directly navigate to leave processing page where he can approve and reject leave request.

how can i do this.

Regards

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Sachin Dhingra