If you see a lot of smtp connections or your server gets constantly in spam black lists, maybe you should check if some bot spams through your server.
The are 2 cases of spamming through a box:
1)using unsecure php forms that bots abuse
2)using smtp connection from an outside client
this artice is about the 2nd case,
Did you ever needed to use CTRL-ALT-DEL through a Remote Desktop Connection?
Exporting/Backing up your Certificate/Private Key in IIS (.pfx file format)
A quick and usefull command for checking if a server is under ddos is:
netstat -anp |grep ‘tcp\|udp’ | awk ‘{print $5}’ | cut -d: -f1 | sort | uniq -c | sort -n
Use mod_rewrite and .htaccess file to block user agent libwww-perl. Open your .htaccess file and add rule as follows:
Do the following:
1) Start Internet Information Services Manager or open the Internet Information Services (IIS) snap-in.
2) Expand Server_name, where Server_name is the name of the server, right-click Default SMTP Virtual Server, and then click Properties.