Couple issues with OpenDMARC on Debian 7:

 * fix mail_db_opendmarc_username/mail_db_opendmarc_password variable
   not found.
 * python-mysqldb package is required. Add it to opendmarc task.

roles/mailserver/tasks/dmarc.yml

-- name: Install OpenDMARC milter
-  apt: pkg=opendmarc state=installed update_cache=yes
+- name: Install OpenDMARC milter and related packages
+  apt: pkg={{ item }} state=installed update_cache=yes
+  with_items:
+      - python-mysqldb
+      - opendmarc
 
 - name: Copy OpenDMARC configuration file into place
   template: src=etc_opendmarc.conf.j2 dest=/etc/opendmarc.conf owner=root group=root

vars/user.yml

 # wallabag
 wallabag_salt: TODO
 wallabag_db_password: TODO
+
+mail_db_opendmarc_username: opendmarc
+mail_db_opendmarc_password: TODO