send e-mail without use sendmail

[Ed Greshko]

Frank Cox wrote:
> On Thu, 01 Nov 2007 10:54:56 +0800
> Ed Greshko <Ed.Greshko at greshko.com> wrote:
> 
>> 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.
> 
> I realize that you can have many mailservers cascading in order of availability
> by specifying multiple IP addresses in your MX records.  However, a lot of
> mailservers have only one IP address specified in their MX record with no
> failover listed. It's part of the relevant RFP that the sending system is
> supposed to retry on a failure anyway, so if the system comes back up within X
> number of days the message is still delivered.
> 
>> Sending to IP addresses doesn't scale and isn't manageable.
> 
> Obviously, it doesn't scale that way, but still -- it's legal to have a single
> IP address specified in your MX record and that comes to the same thing, pretty
> much.
> 
> I still don't see the difference.

Well, for one, what happens if the server in question has a dynamic IP
address and when it changes the system updates its DNS records to reflect
the change.  I did that years ago when I only had dynamic IPs for my domain.
 But I was still able to run a mailserver.  If you relied on IPs it wouldn't
work.