A software interface is required between Postfix and ClamAV. The interface we are going to use is ClamSMTP. Postfix is designed to allow external filters to be called to process mail messages and to return the processed data back to postfix for onward delivery. ClamSMTP has been designed to work directly between Postfix and ClamAV to ensure a simple and reliable implementation.
ClamSMTP is an SMTP filter for Postfix and other mail servers that check for viruses using the ClamAV antivirus software. It is lightweight, reliable, and simple, without a myriad of options. It is written in C without major dependencies.