make extra header checks configurable

README.md

@@ -67,6 +67,11 @@ mydestination: []
 
 # Check quota with dovecot at 127.0.0.1:12340
 check_dovecot_quota: false
+
+# Header checks (only header_checks and mime_header_checks supported), see http://www.postfix.org/header_checks.5.html
+# privacy related headers are removed in any case, you can add more like this:
+add_header_checks:
+    - { regexp: "^Mime:", action: "IGNORE" }
 ```
 
 **postfixmaps**