E2K…Duplicate e-mail

A user tried sending large e-mail but he was not successful. After that he started getting a message, “Some messages couldn’t be retrieved from server. This usually happens when the connection to Server is lost due to server of network problems. If the problem persists, contact your administrator.”

Currently no limit set up for out going or incoming mail size.

Every day since that, he has been getting the same bunch of E-mails over and over. He delete them, and get the same email the next day. What do I need to do to solve this problem?

Thank you,