+ # optional: Domains for which to receive emails and forward according to virtual_alias_map.
+ alias_domains: staff.example.org
+ # optional: Hostnames and SHA1 certificate hashes that are allowed to relay email via this host.
+ relay_client_cert_whitelist:
+ - hostname: other.example.org
+ cert: 00:11:22:33:44:55:66:77:88:99:AA:BB:CC:DD:EE:FF:00:11:22:33
+ # optional: Configure a host to relay all outgoing email to.
+ # Incompatible with smtp_outgoing.
+ relay_host: mx.example.org
+ # optional: Files in /etc/postfix ($FILE.crt, $FILE.key) to use as client certificates when
+ # relaying to the relay_host.
+ relay_client_cert: client_cert