Is your email server on any known blacklist?
Are there probems sending to an email address?
Is email address valid (RFC-2822 compliant)?
Find MX server(s) for a domain
Perform advanced DNS lookups.
Whois lookup (RFC-954 compliant)
Find the location of an IP
Ping an IP or host from the internet.
Trace the route of an IP or host from the Internet
Connect to a port from the Internet.
Type a URL to validate HTML
Start typing to test a password's strength