diff --git a/README.md b/README.md
index 20cb200..e50764f 100644
--- a/README.md
+++ b/README.md
@@ -25,6 +25,7 @@ services:
       - 8007:8007
     environment:
       - ROOT_PASSWD="password"
+      - POSTFIX_RELAY_HOST=""
     volumes:
       - ./data/etc-proxmox-backup:/etc/proxmox-backup
       - ./data/var-lib-proxmox-backup:/var/lib/proxmox-backup
diff --git a/entrypoint.sh b/entrypoint.sh
index 539a3ec..71770a9 100644
--- a/entrypoint.sh
+++ b/entrypoint.sh
@@ -11,7 +11,7 @@ chmod -R 700 /datastore
 #Change postfix config
 sed -i "s/smtp      unix  -       -       y       -       -       smtp/smtp      unix  -       -       n       -       -       smtp/g" /etc/postfix/master.cf
 sed -i "s/docker_hostname/$(hostname)/g" /etc/postfix/main.cf
-sed -i "s/\#relayhost = /\relayhost = $(POSTFIX_RELAY_HOST)/g" /etc/postfix/main.cf
+sed -i "s/\#relayhost = /relayhost = ${POSTFIX_RELAY_HOST}/g" /etc/postfix/main.cf
 
 #Set password from environment variable
 echo "root:$ROOT_PASSWD" | chpasswd