If I understand you correctly, you're asking for the IP addresses of all of our HMOL servers? You only need be concerned with the one where your VHM resides, which should be visible in the address bar of your browser once you've logged on. It will be something along the lines of "hm-uswest51-07.aerohive.com". You can then lookup the IP address of your server, if you need an IP address for your firewall filters.
We've had more than one request for the devices themselves to send email since I started at Aerohive. The decision to use HiveManager as the sending agent predates me, but I imagine it was due to a desire to keep resources on the APs themselves freed up for other tasks.