What happens when you ask Gmail's SMTP server for help?
Transcript of a session with Gmail's SMTP server. Items in italics are my entries.
Traditionally, the HELP command in the SMTP protocol would generate a list of commands supported by the mail server. Most mail servers today simply ignore the command. Google, naturally, points the client to the appropriate RFC—retrieved with nothing less than a Google I'm Feeling Lucky search...bowser:~> telnet gsmtp183.google.com 25 Trying 220.127.116.11... Connected to gsmtp183.google.com. Escape character is '^]'. 220 mx.google.com ESMTP h6si2778348nfh.21 HELO localhost 250 mx.google.com at your service HELP 214 2.0.0 http://www.google.com/search?btnI&q=RFC+2821 h6si2778348nfh.21 QUIT 221 2.0.0 closing connection h6si2778348nfh.21 Connection closed by foreign host.