Sieve addheader directive works only partially

Hi all,

I want to add a custom header to incoming emails from a particular sender. This is what my user Sieve script looks like:

require “editheader”;

if address :is "From” “special-sender@example.com” { addheader “X-My-Custom-Header” “Header Value"; }

I have enabled the editheader extension in my Dovecot configuration:

plugin { … sieve_extensions = +editheader }

This doesn’t seem to work and no header is added to the email. However, if I also move the email to a different folder in the same if-block, the header gets added just fine:

require “editheader”; require “fileinto”;

if address :is "From” “special-sender@example.com” { addheader “X-My-Custom-Header” “Header Value”; fileinto “MyFolder”; }

Am I missing something?

Thanks Peter