--- app/models/channel/email_build.rb.orig      2021-07-27 18:03:57.295467567 +0200
+++ app/models/channel/email_build.rb   2021-07-27 18:04:20.705471697 +0200
@@ -62,6 +62,7 @@
 
       # generate plain part
       attr[:body] = attr[:body].html2text
+      html_alternative = false
     end
 
     # add plain text part