diff --git a/pmg-mail-filter.adoc b/pmg-mail-filter.adoc
index 6fc6b4e..e071f83 100644
--- a/pmg-mail-filter.adoc
+++ b/pmg-mail-filter.adoc
@@ -162,6 +162,10 @@ Disclaimer
 
 Add a Disclaimer.
 
+The disclaimer can contain html markup and will be added to the first found
+text/html and text/plain part of an email. It only gets added if the disclaimer
+text can be encoded in the mail's character encoding.
+
 
 [[pmg_mailfilter_who]]
 'Who' - objects