I am wondering if the iRedMail install has a feature for encrypted secure emails? In particular I mean similar to the manner that some online webmail services provide, such as: hushmail, zixmail, and 4securemail. These send an email to the recipient who then logs in over the internet to read the message -- there is a password challenge or security questions.
The goal is to meet modern email security requirements, such as HIPAA.
This said, hushmail is so inexpensive, it may not be worth the trouble.