Email vs messaging paradigm (patient portal)

I am building a secure patient portal through which patients / doctors communicate. The existing web-based platform fits the traditional "email," paradigm (inbox, sent, archived). Each email has its own subject, body, and thread. I'm wondering however, if there is research that suggests a "Facebook-messenger-like," style is the better model for mail. I don't want to confuse this with synchronous chat, which we also offer. Rather, it's a scrollable thread with your clinician where everything is contained, rather than split into collapsed messages like in an email chain. Advantages / disadvantages you are seeing? Any research?