diff --git a/tasks/main.yml b/tasks/main.yml
index f9ccc70..1b1d2f6 100644
--- a/tasks/main.yml
+++ b/tasks/main.yml
@@ -15,14 +15,14 @@
       MYDESTINATION: >-
         {{ postfix_unix_domains |
         union( [ ansible_fqdn, 'localhost.localdomain', 'localhost'] ) |
-        difference( postfix_mail_domains ) }}
+        difference( postfix_mail_domains ) | join(', ') }}
       MYHOSTNAME:
         "{{ postfix_server_name }}"
       MYDOMAIN:
         "{{ postfix_server_domain }}"
       MYNETWORKS: >-
         {{ ['127.0.0.0/8', '[::ffff:127.0.0.0]/104', '[::1]/128'] |
-        union( postfix_local_networks ) }}
+        union( postfix_local_networks )  | join(', ') }}
       VIRTUAL_ALIAS_MAPS: >-
         {% for d in postfix_mail_domains.keys()|list %}
         {% set p = postfix_mail_domains[d].alias_lookup.provider|default(postfix_lookup_provider) %}