diff --git a/run.sh b/run.sh
index 71a12a9..e0c9462 100644
--- a/run.sh
+++ b/run.sh
@@ -3,6 +3,7 @@
 [ -z "${SMTP_SERVER}" ] && echo "SMTP_SERVER is not set" && exit 1
 [ -z "${SMTP_USERNAME}" ] && echo "SMTP_USERNAME is not set" && exit 1
 [ -z "${SMTP_PASSWORD}" ] && echo "SMTP_PASSWORD is not set" && exit 1
+[ -z "${SERVER_HOSTNAME}" ] && echo "SERVER_HOSTNAME is not set" && exit 1
 
 #Get the domain from the server host name
 DOMAIN=`echo $SERVER_HOSTNAME |awk -F. '{$1="";OFS="." ; print $0}' | sed 's/^.//'`