A system, method and computer program product are provided for identifying spoofed emails. According to the method, an email addressed to a recipient in a first network is received, with the email including a plurality of headers, and at least one of the plurality of headers including a sender address. It is determined whether the sender address indicates a mailbox from within the first network, and the sender address is modified if it indicates a mailbox within the first network. The email with the modified sender address is sent to the recipient. In one embodiment, a second email is received that is from the recipient and that is addressed to the modified sender address, the modified sender address is modified so as to return it to its original form, and the second email is sent.