diff --git a/PORTS.md b/PORTS.md
index 851099d..d24dc95 100644
--- a/PORTS.md
+++ b/PORTS.md
@@ -7,6 +7,6 @@
 - 9000 is the Prometheus port.
   - Every exporter topic must use 90N0-90N9.
   - For example, Node exporter can be on 9010.
-    Dovecot can be on 9020, Postfix can be on 9011,
+    Dovecot can be on 9020, Postfix can be on 9021,
     and so on.
 - Haven't decided on redis, kresd etc. ports yet.