Update to Drupal 8.0.0 beta 14. For more information, see https://drupal.org/node/2544542

core/modules/contact/migration_templates/d6_contact_category.yml

@@ -0,0 +1,22 @@
+id: d6_contact_category
+label: Drupal 6 contact category configuration
+migration_tags:
+  - Drupal 6
+source:
+  plugin: d6_contact_category
+process:
+  id:
+    -
+      plugin: machine_name
+      source: category
+    -
+      plugin: dedupe_entity
+      entity_type: user_role
+      field: cid
+      length: 32
+  label: category
+  recipients: recipients
+  reply: reply
+  weight: weight
+destination:
+  plugin: entity:contact_form

core/modules/contact/migration_templates/d6_contact_settings.yml

@@ -0,0 +1,22 @@
+id: d6_contact_settings
+label: Drupal 6 contact configuration
+migration_tags:
+  - Drupal 6
+source:
+  plugin: d6_contact_settings
+  variables:
+    - contact_default_status
+    - contact_hourly_threshold
+process:
+  user_default_enabled: contact_default_status
+  'flood/limit': contact_hourly_threshold
+  default_form:
+    plugin: migration
+    migration: d6_contact_category
+    source: default_category
+destination:
+  plugin: config
+  config_name: contact.settings
+migration_dependencies:
+  required:
+    - d6_contact_category