diff --git a/README.md b/README.md
index a84d7d7..3ae55f0 100644
--- a/README.md
+++ b/README.md
@@ -72,3 +72,12 @@ group = "mail"
 ```
 
 Then follow the end of the [Official Installation Guide](https://stalw.art/docs/install/docker#take-note-of-the-administrator-password).
+
+Note: Explicitely disable implicit TLS for the smtp listener
+or it may listen for implicit SSL connections instead of StartTLS.
+```
+[server.listener."smtp"]
+bind = ["[::]:25"]
+protocol = "smtp"
+tls.implicit = false
+```