On 2018-04-20 at 20:09 -0400, Viktor Dukhovni via Exim-dev wrote:
> Question about this "$host". Are smarthost settings ever subject to
> MX lookups, so that the actual remote SMTP server is one of the MX
> hosts of the smarthost domain?
Not with the format specified in the example configuration. It would
require explicit configuration action to subject them to MX.
The SMTP Transport is given a list of valid hostnames to try. It knows
nothing about MX lookups.
The `dnslookup` Router driver knows about MX lookups and is how they're
normally done. Here though, we're using the `manualroute` Router
driver.
<
https://www.exim.org/exim-html-current/doc/html/spec_html/ch-the_manualroute_router.html>
It's possible to follow the specified hostname with `/MX` to enable MX
lookups. That doesn't make much sense for smarthost. We can consider
adding some text explicitly warning people against that.
-Phil
