diff --git a/docs/first_steps.md b/docs/first_steps.md
index 21c418db..ab7876dc 100644
--- a/docs/first_steps.md
+++ b/docs/first_steps.md
@@ -136,6 +136,29 @@ server {
 }
 ```
 
+## Optional: Setup a relayhost
+
+Insert these lines to `data/conf/postfix/main.cf`. "relayhost" does already exist (empty), just change its value.
+```
+relayhost = [your-relayhost]:587
+smtp_sasl_password_maps = hash:/opt/postfix/conf/smarthost_passwd
+smtp_sasl_auth_enable = yes
+```
+
+Create the credentials file:
+```
+echo "your-relayhost username:password" > data/conf/postfix/smarthost_passwd
+```
+
+Run:
+```
+docker-compose exec postfix-mailcow postmap /opt/postfix/conf/smarthost_passwd
+docker-compose exec postfix-mailcow chown root:postfix /opt/postfix/conf/smarthost_passwd /opt/postfix/conf/smarthost_passwd.db
+docker-compose exec postfix-mailcow chmod 660 /opt/postfix/conf/smarthost_passwd /opt/postfix/conf/smarthost_passwd.db
+docker-compose exec postfix-mailcow postfix reload
+```
+
+
 ## Install a local MTA
 
 The easiest option would be to disable the listener on port 25/tcp.