We have just set up a new SBS2011 server that gets its email via SMTP. Its the first one ive done that receives mail directly, normally I prefer to collect with POP3.
My worry is that to allow mail to connect to port 25 I have to set the receive connector in exchange to accept mail from IP's 0.0.0.0-255.255.255.255, so basically anyone can connect to it.
1. Whats to stop someone doing a port scan and then abusing the open port 25?
2. By default is the server protected against relaying?
3. Should there be anyhting else I should be checking?
Thank you for your time