I am running a Windows 2003 server with MailEnable 2.0 (I know it's old, but it's a production server and difficult to upgrade).
The server only allows relaying from local IP addresses, but this is without authentication so that scripts (websites) located on the server can send email. It does not allow authentication-based relay because this is not a general mail server and there's no need for that.
Someone has recently begun sending spam from the server, through a script which I cannot identify. I would like to force every sender to at least use a local 'from' address, but checking this option in MailEnable (under SMTP properties > Relay) basically means that people can send email "from" local addresses OR from the local IP, not AND like I would hope.
Please suggest how I can go about either tracking down or blocking the spammer without hurting the ability of other websites to send email. Thanks in advance.