Ensure that dovecot doesn't bind v6 if not required

core/dovecot/conf/dovecot.conf

@@ -6,6 +6,11 @@ protocols = imap pop3 lmtp sieve
 postmaster_address = {{ POSTMASTER }}@{{ DOMAIN }}
 hostname = {{ HOSTNAMES.split(",")[0] }}
 submission_host = {{ FRONT_ADDRESS }}
+{%- if SUBNET6 -%}
+listen = *,::
+{%- else -%}
+listen = *
+{%- endif %}
 
 default_internal_user = dovecot
 default_login_user = mail

core/nginx/dovecot/proxy.conf

@@ -21,6 +21,12 @@ imap_urlauth_host=
 lmtp_proxy = yes
 lmtp_client_workarounds = whitespace-before-path mailbox-for-path
 
+{%- if SUBNET6 -%}
+listen = *,::
+{%- else -%}
+listen = *
+{%- endif %}
+
 default_internal_user = dovecot
 default_login_user = mail
 default_internal_group = dovecot

towncrier/newsfragments/2906.bugfix

@@ -1,2 +1,3 @@
 Switch the admin container from port 80 to port 8080. This should solve issues related to capabilities not working as expected
 Document that systemd-resolve may need to be configured to validate DNSSEC
+Ensure that dovecot is not attempting to bind a v6 socket if SUBNET6 is not configured