[PATCH pmg-docs 6/6] mail proxy: networks: document automatically trusted networks

[Carsten Haerle <carsten.haerle@straightec.de>]

Document which networks are trusted in addition to the configured ones,
the new 'Trust Local Network' option and that host names of the default
relay and transport hosts are resolved when the configuration is
generated.

Signed-off-by: Carsten Haerle <carsten.haerle@straightec.de>
---
 pmgconfig.adoc | 15 +++++++++++++--
 1 file changed, 13 insertions(+), 2 deletions(-)

diff --git a/pmgconfig.adoc b/pmgconfig.adoc
index 00a988e..1269021 100644
--- a/pmgconfig.adoc
+++ b/pmgconfig.adoc
@@ -578,8 +578,19 @@ endif::manvolnum[]
 You can add additional internal (trusted) IP networks or hosts.  All hosts in
 this list are allowed to relay.
 
-NOTE: Hosts in the same subnet as {pmg} can relay by default and don't need to
-be added to this list.
+In addition, the following networks are trusted automatically. They are shown
+greyed out in the list and cannot be edited there:
+
+* The network of the node's IP address, so hosts in the same subnet as {pmg} can
+  relay by default and don't need to be added to this list. You can disable
+  this with the option 'Trust Local Network' under 'Mail Proxy -> Options'.
+  Then only the networks in this list and the hosts below are trusted.
+
+* The default relay and the hosts of all transports, as they are the mail
+  servers that send outgoing mail through {pmg}. Host names are resolved when
+  the configuration is generated, that is, on configuration changes and at
+  boot. If the address of such a host changes, it is only updated with the next
+  configuration change.
 
 
 [[pmgconfig_mailproxy_tls]]
-- 
2.53.0