I am running Virtualmin Pro on my CentOS 6 x64 server and have been running well for quite some time now. One of my sites, clients.airshock.net, is hosted on a server other than the machine where Virtualmin is installed, and is home to the client portal (shopping cart, billing system, etc.) for my company. The site is on a separate server so that, in he event the Virtualmin server becomes unavailable, clients can still log in to check system announcements and etc.
Anyway, I've configured the client portal software to send mail via the Virtualmin server and to use SMTP authentication via a username and password that I've set up in Virtualmin @airshock.net.
The problem arises when the client portal software actually tries to send mail. I always end up seeing a "Relay access denied" error in my mail logs and in the activity logs generated by the software.
Basically, the script at clients.airshock.net is trying to send mail through my Virtualmin server to users at Gmail, Yahoo, and other addresses, using SMTP authentication.
Is this possible? If so how do I fix the "Relay accesss denied" error?