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

[Grant Edwards <grant.b.edwards@gmail.com>]

On 2018-01-20, Grant Taylor <gtaylor@tnetconsulting.net> wrote:
> On 01/19/2018 04:58 PM, Grant Edwards wrote:
>
>> That would require seperate outbound transports that are selected based 
>> on how the mail was read: smtp vs. /usr/bin/sendmail (the real one).
>
> Okay....
>
>> I get the impression from exim and postfix docs that outbound routing 
>> based on input method aren't possible (I may be wrong about that).
>
> Depending on what exactly you're needing, I might be able to think of a 
> way to do this with Sendmail.  -  This may be one of the exceedingly 
> rare times that Sendmail's splitting MTA and MSA roles may actually be 
> beneficial (other than for the security reasons).

[...]

> Am I regurgitating this properly?
>
> 1) You want incoming SMTP connections to go out via your custom mailer 
>    script.
>
> 2) You want messages originated locally and piped into $commandTBD to 
>    go out via SMTP.

Yes -- the two are completely unrelated and unconnected.

> Would I be correct in assuming that the path and / or name of the 
> sendmail like script that interfaces with the Exchange server could 
> change if necessary? I.e. you could name it
> /usr/local/bin/sendmail_to_exchange_gateway if you needed to.

Yes.  It's not actually located at /usr/bin/sendmail, and doesn't need
to be.

> Question:  What name are your scripts currently calling to interface 
> with msmtp?  -  Can that name change if necessary?

Yes they can be changed.  Most of the things that invoke msmtp invoke
it as /usr/bin/msmtp.  A few invoke it as /usr/bin/sendmail.

> I'm trying to juggle the various pieces as I understand them to see if 
> everything can work together.

Don't waste any time on it -- I think the current SMTP server combined
with stunnel is going to work.

> Note:  I'm not trying to push Sendmail.  -  I know I'm strange in my 
> predilection for it.  -  I'm simply trying to solve the problem (as I 
> understand it) with the tools that I know.
>
>> Well I have several msmtp "accounts" set up and run multiple mutt 
>> configurations that use those different accounts for outbound mail.
>
> The different accounts outbound may complicate things.  Are those 
> accounts configured as part of msmtp?  Or are they configured in the 
> things using msmtp?

Both.  msmtp has a config file that defines the accounts, and things
that invoke msmtp directly (e.g. mutt) use a command-line option to
specify an account. There is a default account that's used if the
command line option isn't present (which would be the case for apps
that invoke msmtp as '/usr/bin/sendmail').  Now that I think about it,
I think a configuration that chooses outbound routes for locally
generated email based on from address could work.  Several of those
accounts/routes actually go to the same SMTP server but authenticate
with different username/password combinations.

In mutt's case, I also believe I could switch from msmtp to mutt's
"new" built-in SMTP client code.

Another option would be to set up a container in which to run the
"relay" MTA (sendmail/exim/postfix) that's doing SMTP -->
sendmail-like-script. This is probably the cleanest way to do it.

But, that's all moot if the stunnel solution works.

-- 
Grant