Much of the Internet is protected
with ``paper padlocks.''  Respect them.
No password guessing, network attacks, mailbombing, spoofing, smurfing,
ping-flooding.  No developing or launching worms, viruses, Trojan Horses,
memes, or other hostile messages.  No SMTP server ``hijacking.''
(We have <a href="http://www.postfix.org/">a great SMTP server</a>
right here.  Use it!)  No Web pages that are designed to crash
browsers or otherwise interfere with the visitor's enjoyment of
her system and our Web sites.  Refresh time = 0 stopped being funny
long ago.

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You are, however, allowed to test other people's SMTP servers to discover
whether they allow third party relaying, <em>provided that you make a reasonable
effort to inform their owners of any open relays you find</em>.
You may also use SMTP's EXPN and VRFY commands to try to discover
administrator addresses on a machine that has been used to spam you
or house a spammer.  And of course whittling down a URL
is not anything like password guessing, it's more like ordinary Web navigation.