Use subdomain for srs

defaults/main.yml

@@ -22,6 +22,8 @@ mailserver:
       drop_user_agent:
         regex: '^User-Agent:'
         action: IGNORE
+  postsrsd:
+    srs_domain: "srs.{{ inventory_hostname }}"
   dovecot:
     debug: false
   postfixadmin:

templates/postsrsd/default.j2

@@ -4,7 +4,7 @@
 # Addresses are rewritten to originate from this domain. The default value
 # is taken from `postconf -h mydomain` and probably okay.
 #
-#SRS_DOMAIN=
+SRS_DOMAIN={{ mailserver.postsrsd.srs_domain }}
 
 # Exclude additional domains.
 # You may list domains which shall not be subjected to address rewriting.