send e-mail without use sendmail

[Ed Greshko]

Frank Cox wrote:
> On Wed, 31 Oct 2007 12:05:11 -0500
> Les Mikesell <lesmikesell at gmail.com> 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...

It is call "fault tolerance".  In general, sending to a single IP address is
has a single point of failure.  If that system is down...email doesn't move.
 When you send to company.com there is what is known as an MX record that
returns all the IP addresses that accept email for company.com and weights
for the sending side to decided who to sent to first and failing that
second, etc.

Sending to IP addresses doesn't scale and isn't manageable.