What are the best email encryption services?

RMail® is the e-security platform by RPost®, a global leader since 2000. RMail specializes in elegantly easy to use email encryption for privacy and compliance, e-signatures, legal e-delivery proof, secure file sharing, email impostor protection, document rights management, and AI-infused services to prevent data leaks and human e-security errors. RMail’s transmission e-security services are most often used by businesspeople or business systems that send important, sensitive, or consumer-regulated information. These RMail services are generally applied to those messages where the sender needs functionality beyond standard email in terms of (a) easier to use and more automated email encryption for privacy compliance, (b) returning a verifiable proof record of who said what to whom by email, (c) assurance and peace of mind related to delivery and open status of important and time-deadline email, (d) need a timestamped proof of content delivered, (f) need to share large files securely, or (g) need to easily obtain a recipient e-signature on a sent document.