diff --git a/haraka.sh b/haraka.sh
index 9fc1bdd..1ffe73b 100644
--- a/haraka.sh
+++ b/haraka.sh
@@ -9,11 +9,13 @@ fi
 echo $HOSTNAME > /haraka/config/me
 
 # Get and install certificates from Let's Encrypt
-certbot certonly -n --agree-tos -d "$HOSTNAME"
-mkdir -p /haraka/config/tls
-cd /haraka/config/tls
-ln -s /etc/letsencrypt/live/$HOSTNAME/privkey.pem tls-key.pem
-ln -s /etc/letsencrypt/live/$HOSTNAME/fullchain.pem tls-cert.pem
-cd -
+if [ ! -f /haraka/config/tls ]; then
+  certbot certonly -n --agree-tos -d "$HOSTNAME" --standalone --preferred-challenges http
+  mkdir -p /haraka/config/tls
+  cd /haraka/config/tls
+  ln -s /etc/letsencrypt/live/$HOSTNAME/privkey.pem tls-key.pem
+  ln -s /etc/letsencrypt/live/$HOSTNAME/fullchain.pem tls-cert.pem
+  cd -
+fi
 
 haraka -c /haraka