check for local_mx only when default route is used

[analogic]

github somehow broke the #3300 PR - still showing me "processing updates" and refusing to accept changes, so this is a second attempt to update cfg.local_mx_ok functionality

It only checks local mx if it falls through to the default route - so any plugin's mx is excluded.

[msimerson]

👍 I like this approach better than #3300. I'd like to consider it for another day or two, and give others a chance to weigh in.

[msimerson]

The bit of code you had to change in found_mx I find to be clumsy (manually copying over every property). Instead, how about improving that code with Object.assign:

diff --git a/outbound/hmail.js b/outbound/hmail.js
index 68f57f72..1a817fd7 100644
--- a/outbound/hmail.js
+++ b/outbound/hmail.js
@@ -272,15 +272,11 @@ class HMailItem extends events.EventEmitter {
                 if (mxlist[mx].path) {
                     this.mxlist.push(mxlist[mx]);
                 }
-                else if (obc.cfg.ipv6_enabled) {
-                    this.mxlist.push(
-                        { exchange: mxlist[mx].exchange, priority: mxlist[mx].priority, port: mxlist[mx].port, using_lmtp: mxlist[mx].using_lmtp, family: 'AAAA' },
-                        { exchange: mxlist[mx].exchange, priority: mxlist[mx].priority, port: mxlist[mx].port, using_lmtp: mxlist[mx].using_lmtp, family: 'A' }
-                    );
-                }
                 else {
-                    mxlist[mx].family = 'A';
-                    this.mxlist.push(mxlist[mx]);
+                    this.mxlist.push(Object.assign({}, mxlist[mx], { family: 'A' });
+                    if (obc.cfg.ipv6_enabled) {
+                        this.mxlist.push(Object.assign({}, mxlist[mx], { family: 'AAAA' });
+                    }
                 }
             }
             this.try_deliver();

or even better still, use the es6 spread operator:

this.mxlist.push({ ...mxlist[mx], ...{ family: 'A' });
if (obc.cfg.ipv6_enabled) {
  this.mxlist.push({ ...mxlist[mx], ...{ family: 'AAAA' });
}

[msimerson]

I'm trying hard to like the name default here. It's not very self documenting and requires one to go figure out how default got set. In this case, default means "looked up via DNS". But that's a bit long for a name. Perhaps something like from_dns or via_dns, so the if reads something like "if the mx was looked up in DNS and ! local_mx_ok)". That'll also avoid namespace collisions when someone goes searching to find how that property got set.

[analogic]

I don't like default either, naming is hard...