Re: [gentoo-user] Re: Simple SMTP to cmd-line MTA relay?

[Grant Taylor]

On 01/19/2018 11:31 AM, Grant Edwards wrote:
> I want to accept incoming email via SMTP (my computer is an SMTP server).

Okay.

So you don't need to accept mail via /usr/sbin/sendmail (et al).

Or rather, that's what you want email to leave the relay through.

> I want to relay each of those messages by invoking a command-line utility
> that has the same "API" as /usr/bin/sendmail.  That utility injects the
> mail into another machine's MTA.

Okay.

Aside:  I don't know that I would consider that to be an API, but I do 
see why you consider it as such.

> In this case, the /usr/bin/sendmail utility transfers the message to a
> different machine's MTA using mechanisms that are beyond the scope of
> my question.

Okay.

> There is no local delivery.  It is a relay that accepts mail via SMTP and
> transfers it to a different MTA.  The usual way to do this is to accept
> mail as an SMTP server and then relay it to the next MTA by acting as
> an SMTP client (e.g. via postfix's 'relayhost' setting).
>
> Instead of transfering mail to the next MTA by acting as an SMTP client,
> I want to transfer it by invoking a command-line utility like sendmail
> or msmtp.

So it sounds to me like you want a gateway of sorts that speaks SMTP (as 
a server to clients) on one side and <some custom non-SMTP method> (that 
acts as a client to other servers) on the other side.  Is that accurate?

In Sendmail parlance, what you want is a custom mailer.  Said custom 
mailer would then interface with your custom /usr/bin/sendmail 
(emulation wrapper).

Finally, configure Sendmail to use said custom mailer as the method to 
communicate with the smart host.



-- 
Grant. . . .
unix || die