Originally posted by guano
Looking at the MX record information for the defcon.org domain reveals the following:
defcon.org mail exchanger = 10 mail-1.datamerica.com.
defcon.org mail exchanger = 20 mail-2.datamerica.com.
Checking for service running on the standard mail port for MX host entries in order of precedence:
$ telnet mail-1.datamerica.com 25
Trying 216.231.63.44...
Connected to mail-1.datamerica.com.
Escape character is '^]'.
220 colossus.datamerica.com ESMTP Sun, 30 May 2004 12:48:33 -0700 (PDT)
500 5.5.1 Command unrecognized: ""
quit
221 2.0.0 colossus.datamerica.com closing connection
Connection closed by foreign host.
and
$ telnet mail-2.datamerica.com 25
Trying 216.231.63.45...
Connected to mail-2.datamerica.com.
Escape character is '^]'.
220 guardian.datamerica.com ESMTP Sun, 30 May 2004 05:42:41 -0700 (PDT)
500 5.5.1 Command unrecognized: ""
quit
221 2.0.0 guardian.datamerica.com closing connection
Connection closed by foreign host.
shows that there is a service listening on the SMTP port for both MX hosts.
Your Mail message bounce states that your mail relay/host was Persistent Transient Failure.
If this is a caching issue of your ISP, you can always try registering an account at hotmail, yahoo, etc. and see if delivery issues persist when you mail them from that location. If that message works while mail from through your ISP SMTP relay fails, then complain to your ISP.
HTH
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