MS Exchange 2010 - Read receipt

In my Organization we have exchange server 2010 and user is accessing mails by configuring in Outlook 2010(POP3)

User 1 is sending mail with read receipt to User 2 

Once User 2 is receiving the mail then user 1  receives the read receipt notification (User 2 is not opening and read the mail but User 1 receives the read receipt notification)

Problem is User2 is not opening and read the mail just received but user1 receives the read receipt notification 

Kindly help us to solve this

Thanks !