Skip SPF check for outbound mail when context is not 'myself'

[gramakri]

Fixes #1762

[msimerson]

The edge case I see with this change affects orgs that have to send all their emails via a 3rd party (typically their ISP) mail server. Think of a small local business with an internal mail server who has outbound port 25 blocked by their ISP (this is not unusual). In that case, they set up their MTA to relay through their ISP. Their SPF records cover their and their ISPs mail server and everyone is happy. I can't see any reason not to evaluate SPF in that case.

If you were to amend this PR such that it disabled the same check but only for private IP space (see attached diff), then I'd +1 that.

diff --git a/plugins/spf.js b/plugins/spf.js
index 0e880e7..0e55915 100644
--- a/plugins/spf.js
+++ b/plugins/spf.js
@@ -114,9 +114,10 @@ exports.hook_helo = exports.hook_ehlo = function (next, connection, helo) {
 exports.hook_mail = function (next, connection, params) {
     var plugin = this;
 
-    // For inbound message from a private IP, skip MAIL FROM check
-    if (!connection.relaying && connection.remote.is_private) {
-        return next();
+    // For messages from private IP space...
+    if (connection.remote.is_private) {
+        if (!connection.relaying) return next();
+        if (connection.relaying && plugin.cfg.relay.context !== 'myself') return next();
     }
 
     var txn = connection.transaction;

[gramakri]

@msimerson Thanks for the review. I have modified the patch accordingly.

[msimerson]

+1