If you install McAfee VirusScan Enterprise on an Exchange Server you will find that your outbound mail is being blocked. By default McAfee only allows certain processes to send out on port 25. Exchange isn’t one of them.
The block is caused by the Access Protection component. Disabling this component entirely would allow your mail to flow again. However, disabling an entire protection component may not be ideal. Instead we list a couple of options below to allow Exchange through without sacrificing security.
Right click on the McAfee taskbar icon and select VirusScan console from the context menu.