added warning message for PERMIT_DOCKER=network when using IPv6 (dock…

…er-mailserver#1405)
polarathene · Sep 27, 2020 · 5d992f9 · 5d992f9
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commit 5d992f9
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diff --git a/Installation-Examples.md b/Installation-Examples.md
@@ -1,5 +1,7 @@
 ## Building a simple mailserver
 
+**WARNING**: Adding the docker network's gateway to the list of trusted hosts, e.g. using the `network` or `connected-networks` option, can create an [**open relay**](https://en.wikipedia.org/wiki/Open_mail_relay), [for instance](https://github.com/tomav/docker-mailserver/issues/1405#issuecomment-590106498) if IPv6 is enabled on the host machine but not in Docker. ([#1405](https://github.com/tomav/docker-mailserver/issues/1405))
+
 We are going to use this docker based mailserver:
 
 - First create a directory for the mailserver and get the setup script: