diff --git a/healthchecks/README.md b/healthchecks/README.md
index 5c8d79f..2782a76 100644
--- a/healthchecks/README.md
+++ b/healthchecks/README.md
@@ -2,3 +2,6 @@
 
  A cron monitoring tool written in Python & Django
 
+## Important step when deploying
+The environment variable EMAIL_PORT cannot be left empty.
+For deactivating e-mail, simply set it to -1.