diff --git a/run.sh b/run.sh
index b54fdff..976cc66 100644
--- a/run.sh
+++ b/run.sh
@@ -21,7 +21,7 @@ if [ -n "${SMTP_PASSWORD_FILE}" ]; then [ -f "${SMTP_PASSWORD_FILE}" ] && read S
 [ -z "${SMTP_PASSWORD}" ] && echo "SMTP_PASSWORD is not set" && exit 1
 [ -z "${SERVER_HOSTNAME}" ] && echo "SERVER_HOSTNAME is not set" && exit 1
 
-SMTP_PORT="${SMTP_PORT-587}"
+SMTP_PORT="${SMTP_PORT:-587}"
 
 #Get the domain from the server host name
 DOMAIN=`echo ${SERVER_HOSTNAME} | awk 'BEGIN{FS=OFS="."}{print $(NF-1),$NF}'`