I don't recall any specific issues with compatibility between Clarity and mostly any version of Exchange.
Clarity is just a sender of SMTP mail, doesn't receive, and doesn't directly integrate in any other way.
So even if you did have a problem in a specific setup or configuration, it should be something that can be worked around by adding another mail gateway/proxy between them. Clarity would send mail to the gateway, the gateway could forward to Exchange, and then they'll be delivered from there.
But I doubt you'd even need to go that far.