diff --git a/README.md b/README.md
index 36ced63..dd250b0 100644
--- a/README.md
+++ b/README.md
@@ -13,6 +13,9 @@ The internet domain name of the mail system.
 ## SMTP_BANNER
 Text prepended to `$myhostname ESMTP $mail_name` for the smtp banner.
 
+## SPAMASSASSIN_HOST
+Hostname for the spamassassin host.
+
 ## DOVECOT_HOST
 Hostname for the dovecot host.