BITS usually allows the mail account to be active for 6 months from the date of graduation qualification exams. After 6 months you will receive a mail like this from BITS admin.
Hello,
This is the WILP Mailadmin at BITS, Pilani.
Our records indicate that you have graduated from the institution and are no longer a current student. If this is not correct, please write to mailadmin@wilp.bits-pilani.ac.in immediately with details of your present academic status.
As per the email policy, your BITS Mail account will be deactivated on May 21st 2014 and you will no longer be able to access it after that date. We recommend that you take a backup or migrate your emails, contacts and other data, if any, from your BITS Mail account without further delay.
Please write to mailadmin@wilp.bits-pilani.ac.in for any questions and concerns.