Message delivery incomplete

when I get a email with appendix release is not delivered the mail and I get the following mail

We have re-scanned your message to check for viruses and we have identified that your message has a virus. Hence we have changed the Reason for it being quarantined to “Malware”. If you wish to release this message, you will possibly infect your machine and other machines in the network. We strongly recommend you to not release this message. If you have further questions, please contact your IT administrator.