Fixed table of contents

README.md

@@ -15,8 +15,10 @@ THANK YOU to all of the authors of the content linked to in this wiki!
   - [Categorization and Blacklist Checking Resources](#categorization-and-blacklist-checking-resources)
 - [Redirectors](#redirectors)
   - [SMTP](#smtp)
-    - [Remove previous server headers](#remove-previous-server-headers)
-    - [Configure a catch-all address](#configure-a-catch-all-address)
+    - [Sendmail](#sendmail)
+      - [Remove previous server headers](#remove-previous-server-headers)
+      - [Configure a catch-all address](#configure-a-catch-all-address)
+    - [Postfix](#postfix)
 - [DNS](#dns)
   - [socat](#socat)
   - [iptables](#iptables)