diff --git a/.env.sample b/.env.sample
index 16dde98..7be4e13 100644
--- a/.env.sample
+++ b/.env.sample
@@ -31,3 +31,6 @@ TX="Europe/Berlin"
 #SMTP_HOST=mail.example.com
 #SMTP_PORT=587
 #SMTP_SECURITY=starttls
+# If SMTP isn't working, enable this line to debug
+#  remember to disable it after debugging
+#SMTP_DEBUG=true
diff --git a/compose.smtp.yml b/compose.smtp.yml
index 849812c..9516883 100644
--- a/compose.smtp.yml
+++ b/compose.smtp.yml
@@ -13,6 +13,7 @@ services:
       - "SMTP_HOST"
       - "SMTP_PORT"
       - "SMTP_SECURITY"
+      - "SMTP_DEBUG"
 
 secrets:
   smtp_password: