Re: [exim4] mixed up about terminology
On Wed, 08 Oct 2014 22:41:29 -0400
Jerry Stuckle <jstuckle@attglobal.net> wrote:
> On 10/8/2014 8:17 PM, lee wrote:
> >
> > Ok, and what difference does this actually make?
> >
> >
>
> If you don't know the difference between an MTA and an MUA, there is
> no way I can help you.
>
Humans generally do, the point is that another MTA doesn't know the
difference, nor does it need to. Unless it's been programmed to measure
timings, it can't even tell if it's a human talking to it with a telnet
client. SMTP is SMTP. There are no special commands used to tell an MTA
what type of entity is talking to it.
An MTA will:
a) deliver mail locally if the recipient has a mailbox on the host
b) *relay* to another MTA, if appropriate security criteria are met
c) refuse the message, on various grounds, at various stages of the
SMTP transaction
That's all. And it doesn't care whether the mail has come from a telnet
client, a GUI email application such as Claws, another network MTA or a
workstation's own MTA. Or an SMTP engine in a virus, for that matter.
--
Joe
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