I highly recommend Trend Micro Deep Discovery Email Inspector due to its security and scalability features.
Trend Micro Deep Discovery Email Inspector excels in analyzing phishing emails and offers robust outbound and inbound monitoring, network visibility, and rapid sandboxing technology, rated ten for stability. Recommended for security and scalability, it could improve with lighter network impact, enhanced bulk email handling, quicker issue detection, detailed reporting, and compatibility with older systems. Better technical support is needed for its effective utilization by tech buyers.