docs: `bind-smtp-network-interface.md` - Add bridge network config advice (#4330)

Co-authored-by: Brennan Kinney <5098581+polarathene@users.noreply.github.com>

docs/content/examples/use-cases/bind-smtp-network-interface.md

@@ -21,10 +21,6 @@ This can be configured by [overriding the default Postfix configurations][docs::
 In `postfix-main.cf` you'll have to set the [`smtp_bind_address`][postfix-docs::smtp-bind-address-ipv4] and [`smtp_bind_address6`][postfix-docs::smtp-bind-address-ipv6]
 to the respective IP-address on the server you want to use.
 
-[docs::overrides-postfix]: ../../config/advanced/override-defaults/postfix.md
-[postfix-docs::smtp-bind-address-ipv4]: https://www.postfix.org/postconf.5.html#smtp_bind_address
-[postfix-docs::smtp-bind-address-ipv6]: https://www.postfix.org/postconf.5.html#smtp_bind_address6
-
 !!! example
 
     === "Contributed solution"
@@ -55,14 +51,56 @@ to the respective IP-address on the server you want to use.
         ```
 
         If that avoids the concern with `smtp-amavis`, you may still need to additionally override for the [`relay` transport][gh-src::postfix-master-cf::relay-transport] as well if you have configured DMS to relay mail.
+        
+    === "Bridged Networks"
+    
+        When your DMS container is using a bridge network, you'll instead need to restrict which IP address inbound and outbound traffic is routed through via the bridged interface.
+        
+        For **inbound** traffic, you may configure this at whatever scope is most appropriate for you:
+
+        - **Daemon:** Change the [default bind address][inbound-ip::docker-docs::daemon] configured in `/etc/docker/daemon.json` (default `0.0.0.0`)
+        - **Network:** Assign the [`host_binding_ipv4` bridge driver option][inbound-ip::docker-docs::network] as shown in the below `compose.yaml` snippet.
+        - **Container:** Provide an explicit host IP address when [publishing a port][inbound-ip::docker-docs::container].
+        
+        For **outbound** traffic, the bridge network will use the default route. You can change this by either:
+
+        - [Manually routing networks][outbound-ip::route-manually] on the host.
+        - Use the [`host_ipv4` driver option][outbind-ip::host-ipv4] for Docker networks to force the SNAT (source IP) that the bridged network will route outbound traffic through.
+            - This IP address must belong to a network interface to be routed through it.
+            - IPv6 support via `host_ipv6` [requires at least Docker v25][outbind-ip::host-ipv6].
+
+        ---
+
+        Here is a `compose.yaml` snippet that applies the inbound + outbound settings to the default bridge network Docker Compose creates (_if it already exists, you will need to ensure it's re-created to apply the updated settings_):
+        
+        ```yaml title="compose.yaml"
+        networks:
+          default:
+            driver_opts:
+              # Inbound IP (sets the host IP that published ports receive traffic from):
+              com.docker.network.bridge.host_binding_ipv4: 198.51.100.42
+              # Outbound IP (sets the host IP that external hosts will receive connections from):
+              com.docker.network.host_ipv4: 198.51.100.42
+        ```
 
 !!! note "IP addresses for documentation"
 
-    IP addresses shown in above examples are placeholders, they are IP addresses reserved for documentation by IANA (_[RFC-5737 (IPv4)][rfc-5737] and [RFC-3849 (IPv6)][rfc-3849]_). Replace them with the IP addresses you want DMS to send mail through.
+    IP addresses shown in above examples (`198.51.100.42` + `2001:DB8::42`) are placeholders, they are IP addresses reserved for documentation by IANA (_[RFC-5737 (IPv4)][rfc-5737] and [RFC-3849 (IPv6)][rfc-3849]_). Replace them with the IP addresses you want DMS to send mail through.
-    
+
+[docs::overrides-postfix]: ../../config/advanced/override-defaults/postfix.md
+[postfix-docs::smtp-bind-address-ipv4]: https://www.postfix.org/postconf.5.html#smtp_bind_address
+[postfix-docs::smtp-bind-address-ipv6]: https://www.postfix.org/postconf.5.html#smtp_bind_address6
+
 [rfc-5737]: https://datatracker.ietf.org/doc/html/rfc5737
 [rfc-3849]: https://datatracker.ietf.org/doc/html/rfc3849
 
 [gh-pr::3465::comment-restrictions]: https://github.com/docker-mailserver/docker-mailserver/pull/3465#discussion_r1458114528
 [gh-pr::3465::alternative-solution]: https://github.com/docker-mailserver/docker-mailserver/pull/3465#issuecomment-1678107233
 [gh-src::postfix-master-cf::relay-transport]: https://github.com/docker-mailserver/docker-mailserver/blob/9cdbef2b369fb4fb0f1b4e534da8703daf92abc9/target/postfix/master.cf#L65
+
+[inbound-ip::docker-docs::daemon]: https://docs.docker.com/reference/cli/dockerd/#default-network-options
+[inbound-ip::docker-docs::network]: https://docs.docker.com/engine/network/drivers/bridge/#default-host-binding-address
+[inbound-ip::docker-docs::container]: https://docs.docker.com/reference/compose-file/services/#ports
+[outbound-ip::route-manually]: https://github.com/moby/moby/issues/30053#issuecomment-1077041045
+[outbind-ip::host-ipv4]: https://github.com/moby/libnetwork/pull/2454
+[outbind-ip::host-ipv6]: https://github.com/moby/moby/issues/46469