Freeware: Dnsbl

Anti-Spam Blacklist Thing 1.1Anti-Spam Blacklist Thing lets you check to see if a given IP address or hostname is on one of up to 20 different anti-spam blacklists. Anti-Spam Blacklist Thing is provided by SpamButcher completely free of charge.

No Spam Today! for Servers Freeware 3.0.5.1Mail spam filter (SMTP/POP3) that easily integrates with every mail server software. NoSpamToday! includes the award-winning SpamAssassin filter, an attachment blocker, and an RBL filter. Virus scanners can be integrated into the filtering pipeline.

Web Proxy Checker 1.5.10Free and fast proxy checking software. Supports SOCKS4/SOCKS5/HTTP/HTTPS proxies. Check for connect to host or load URL. Multithreaded. Handle redirects. Can download proxy list from the given URL. Built-in proxy distribution web server.

eWall SMTP Proxy 4.0eWall is a gateway between the Internet and your mail server. It monitors the SMTP traffic in real-time, catching the majority of spam and viruses. The chain of flexible PHP filters stops more than 95% of unwanted emails out of the box.