Email protect is base band (you get Threat and Spam protection), and Safeguard is adding Data Protect, Image Control, Policy based and TLS encryption to the base band.
Email Protect
Provides accurate and effective spam and malware protection with Skeptic™ technology. Skeptic self-learning heuristic technology allows it to detect sophisticated attacks via predictive analysis. Real-Time Link Following is also included to protect against malicious URLs embedded in messages.
Email Safeguard
Includes all the features of Email Protect plus additional privacy and control features. Data Protection includes simple policy templates to address internal, legal, and regulatory compliance needs. Image Control can identify, control, and block inappropriate images from entering or leaving the organization. Policy Based Encryption Essentials and TLS Encryption links provide secure message transport.
"Service Plans" on this link: