send e-mail without use sendmail

Les Mikesell lesmikesell at
Thu Nov 1 04:02:07 UTC 2007

Frank Cox wrote:
>> You must have a real domain name to send email. 
> Is there any technical reason (other than "we hate spammers") why email can't
> be sent to an IP address instead of a domain name?
> I know that mail sent to joeblow at 123.456.789.001 doesn't work, but have never
> really understood why...

Mail is a special case in DNS since most organizations want delivery to 
be directed to a small number of servers, so the host/domain lookup 
always tries to follow MX records.  If you want to use a literal IP 
address you have to enclose it in []'s to skip the MX lookup (and if you 
are doing it on the command line, enclose in ''s because the []' are 
shell metacharacters). mail 'joeblow@[]' will attempt a 
connection, but the receiving system may still not like it.

   Les Mikesell
     lesmikesell at

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