SMTP Virtual Server questions

I admin an Exchange 2003 Enterprise email server that I didn't setup, it has the IP address set to all unassigned on the default smtp Virtual server TCP port 26 ???? and a Second Virtual Server setup with two port identities of TCP Port 2600 and 25? IP address all unassigned as well. I know some of the POP3 users had their outlook configured for smtp port 2600 but why would it be done this way? The old admin and director have been fired before I got a chance to ask them this. The EBPA tool reports on this as a possible reason for trafic flow issues, we also have smart hosts setup on both so outgoing and incoming mail gets filtered by Postini. I just want to know how it should be done or is it ok this way?
Comments
I would try to find out if this Postini that you refer to is set up to send through your server at port 26. I wouldn't have set it up like that, but you really need to look at everything that might possibly be touching SMTP to get the full picture.
Is logging enabled on the SMTP virtual servers? Searching for those port numbers in the log file might provide some clues too.
Recent: 11/2019 - RHCSA (RHEL 7); 2/2019 - Updated VCP to 6.5 (just a few days before VMware discontinued the re-cert policy...)
Working on: RHCE/Ansible
Future: Probably continued Red Hat Immersion, Possibly VCAP Design, or maybe a completely different path. Depends on job demands...
Check the Connection and the Relay buttons on the Access tab of the different virtual servers. They probably have different settings to allow your POP3 clients to relay through their connections. If they don't, then the previous admins were probably counting on using the alternate ports as a layer of security. This isn't really that safe beacuse a port scan would reveal the port as open and a spammer is one setting change away from using your exchange server as an open relay. If you set the virtual server to only allow computers that authenticate to relay, your users will have to enter a username and password to send mail but you won't be an open relay.
Since you mentioned these are Outlook users, have you considered RPC over HTTP instead of POP3/SMTP for your remote users?
Yes
http://www.petri.co.il/configure_rpc_over_https_on_a_single_server.htm