diff --git a/content/blog/mail_server_alpine_postfix_dovecot_tutorial/index.md b/content/blog/mail_server_alpine_postfix_dovecot_tutorial/index.md
index fe9e42e..cce1033 100644
--- a/content/blog/mail_server_alpine_postfix_dovecot_tutorial/index.md
+++ b/content/blog/mail_server_alpine_postfix_dovecot_tutorial/index.md
@@ -1283,6 +1283,9 @@ smtp-amavis   unix -     -       n       -       2       smtp
   -o smtpd_client_connection_count_limit=0
   -o smtpd_client_connection_rate_limit=0
   -o receive_override_options=no_header_body_checks,no_unknown_recipient_checks,no_address_mappings
+  # avoid double dkim signing by setting smtpd_milters to empty
+  # otherwise will run all milters again after amavis
+  -o smtpd_milters=
 ```
 
 The first block tells Postfix to send emails to Amavis, and the second block tells Postfix to run an extra smtpd daemon