diff --git a/friendica/content.md b/friendica/content.md
index df72f372e..ee06996c4 100644
--- a/friendica/content.md
+++ b/friendica/content.md
@@ -104,11 +104,15 @@ The following environment variables are possible for the SMTP examples.
 -	`SMTP_DOMAIN` The sender domain. (**required** - e.g. `friendica.local`)
 -	`SMTP_FROM` Sender user-part of the address. (Default: `no-reply` - e.g. no-reply@friendica.local)
 -	`SMTP_TLS` Use TLS for connecting the SMTP Mail-Gateway. (Default: empty)
--	`SMTP_STARTTLS` Use STARTTLS for connecting the SMTP Mail-Gateway. (Default: empty)
+-	`SMTP_STARTTLS` Use STARTTLS for connecting the SMTP Mail-Gateway. (Default: `On`)
 -	`SMTP_AUTH` Auth mode for the SMTP Mail-Gateway. (Default: `On`)
 -	`SMTP_AUTH_USER` Username for the SMTP Mail-Gateway. (Default: empty)
 -	`SMTP_AUTH_PASS` Password for the SMTP Mail-Gateway. (Default: empty)
 
+**Addition to STARTTLS**
+
+the `tls_starttls` setting is either `On` or `Off`, but never unset. That's because in case it's unset, `starttls` would be activated by default (which would need additional configuration like a separate port).
+
 ## Database settings
 
 You have to add the Friendica container to the same network as the running database container, e. g. `--network some-network`, and then use `mysql` as the database host on setup.