Configure Firewall to block smtp access to server on internal network
Posted on 2011-05-01
Hello I noticed I have a security flaw in my system whereby if I am located internally of the network and telnet to my mail server I can create an email message and send it without authenticating, thereby allowing users to create a bogus senders address and spam valid senders within our environment. I was looking at potential ways of preventing this from happening. One thought was to to create a lan to lan firewall rule allowing access on port 25 only on the email server, so deny all others lan to lan traffic on port 25 just wasn't sure if I would be impacting on other areas working effectively. for example my proxy server emails out when it has an issue etc. so might need to restrict it to all servers, unless someone else can offer some alternative suggestions to prevent this behaviour. My email system is groupwise 8 and I have a cyberoam firewall.