diff --git a/roles/docker/templates/compose-files/postfix.yml.j2 b/roles/docker/templates/compose-files/postfix.yml.j2
index 6a64111..f460610 100644
--- a/roles/docker/templates/compose-files/postfix.yml.j2
+++ b/roles/docker/templates/compose-files/postfix.yml.j2
@@ -13,7 +13,7 @@ services:
       - "./dkim:/etc/opendkim/keys"
     environment:
       # Get all services which have allowed_sender_domain defined
-      ALLOWED_SENDER_DOMAINS: "{{ services | dict2items | selectattr('value.allowed_sender_domain', 'true') | map(attribute='value.domain') | join(' ') }}"
+      ALLOWED_SENDER_DOMAINS: "data.coop {{ services | dict2items | selectattr('value.allowed_sender_domain', 'true') | map(attribute='value.domain') | join(' ') }}"
       HOSTNAME: "{{ services.postfix.domain }}" # the name the smtp server will identify itself as
       DKIM_AUTOGENERATE: true