service/email.md

@@ -651,6 +651,27 @@ postmap -q user@torproject.org ldap:/etc/postfix/maps/transport_local
 
 This should return `smtp:srs.torproject.org`.
 
+Individual hosts *may* also define aliases with a
+`postfix::profile::alias` define for local, backwards-compatibility
+purposes. This should be considered legacy and typically will not work
+if there is a virtual map override (a common configuration). In that
+case, a local alias may be defined with (say):
+
+```puppet
+  postfix::map { 'virtual':
+    map_dir         => $postfix::map_dir,
+    postmap_command => $postfix::postmap_command,
+    owner           => $postfix::owner,
+    group           => $postfix::group,
+    mode            => $postfix::mode,
+    type            => 'hash',
+    contents        => [
+      'postmaster@example.torproject.org    postmaster@torproject.org',
+      'do-not-reply@example.torproject.org  nobody',
+    ],
+  }
+```
+
 ### SRS
 
 Our SRS servers, currently only srs-dal-01, are managed by the profile::srs manifest.