[Dovecot] [OT] Is there a secure reverse IMAP proxy

This question is off topic. I ask this list because the question is related to security and IMAP and I guess the people in this list know a lot about both of that.

Is there a secure reverse proxy for the IMAP protocol? Something you can install on a bastion host which checks the IMAP traffic before forwarding it to the internal IMAP server?

There are these proxies for WebMail to IMAP connections but as far as I can tell they were not created for security reasons and not with security as primary goal.

Sven