The best feature of mail guard is its ability to scan emails for spam or viruses without opening them. It can be used as a standalone product but i found it more useful when integrated in our cloud service (Office 365). I do not like that you need an account set up at their end before using this software. You also cannot use your own domain if you are integrating the two services together. If you want a fast way to check incoming mails for virus/malware then this is probably one of the most effective ways out there. We have been able to detect phishing attempts from customers within seconds which has helped us mitigate any potential risk.