diff --git a/mco.md b/mco.md
index 6b5b6e5..9079091 100644
--- a/mco.md
+++ b/mco.md
@@ -39,6 +39,7 @@
   * [ ] postqueue -p
   * [ ] pflogsum - sudo pflogsumm /var/log/maillog|less
   * [ ] blacklist check
+   * [ ] check rbl
    * [ ] https://mxtoolbox.com/emailhealth/pole-en-scenes.com/
    * [ ] https://mxtoolbox.com/emailhealth/kafig.com/