We have installed qmail in our new server and started running our website in the server.
It was a dedicated server and did not have much experience in the mail server configuration. So we installed it in the default form.
Now my server people complain that we are sending spam with the server. We have also confirmed the somehow our mail server is used to send some spam emails.
Can anybody send the email using our qmail mail server FROM A DIFFERENT server?
Or will it be somebody hacked into our server and wrote a php program to send the emails?
I doubt the first one anyway?
If so, how can I prevent others to not use the mail server but just allow my own php files to send email with the mail server?
Can anybody please advice?