Received itrv at different email address than given

I filed my returns and received my ITRV via email from incometaxefiling about 2 days later.

But, the ITRV came to a different email address than the one I gave in the form. 

For the past few years I have been using a new email address including for IT returns and received all communication correctly at this new address. But this time for some reason I received the ITRV at an old email address which I haven't used for quite some time. I have never used this email address anywhere in communication with IT Dept or TRACES or eFiling Intermediary etc.

The only way the IT Dept. could have had this address is that I have used it many years ago when applying for a PAN Card.

I dont know why it was used when I clearly used a different email address in the current returns and elsewhere. 

Can anyone please throw some light on why this could have happened?

Thank You.