diff --git a/README.md b/README.md
index bb0ae68..69782f1 100644
--- a/README.md
+++ b/README.md
@@ -209,6 +209,9 @@ printf 'Hello yournamehere!\n I am looking for real IPv6 friends.\n You find my
 And obviously this is waaaaaaaaay to long to type. That's why
 `rif-invitefriends.sh` puts this nicely into a script.
 
+Attention: this requires a working mail setup on your computer
+(i.e. outgoing emails sending by `mail` works).
+
 ## Finding friends
 
 As real IPv6 friends are decentralised, there is no central registry