Security apprehensions about open 1352 port for inbound NPRC traffic

Staff in my organisation using Lotus Notes client in another city need to access a domino server within a firewall.

We understand we need to open port 1352 to achieve this.

My IT Manager is convinced about Lotus Notes data transaction security from the internet to a domino server inside the firewall, but is not convinced about the security of opening port 1352 to the Internet.

Could a hacker come in though port 1352 who does not have a certified id using the notes client or in any other way?

We are not using a VPN.

Could you help me with your experience in such an infrastructure or any literature evidence about the safety of opening port 1352 for inbound NRPC traffic from the Internet.

Thank you in advance.

Subject: *I recommend it and suggest you encrypt the port. We, and our clients, have had servers open to the Internet since the mid-90’s.