diff --git a/group_vars/matrix_servers b/group_vars/matrix_servers
index 9efd1539..e9dbffb5 100755
--- a/group_vars/matrix_servers
+++ b/group_vars/matrix_servers
@@ -655,6 +655,11 @@ matrix_synapse_container_image_self_build: "{{ matrix_container_images_self_buil
 # When ma1sd is enabled, we can use it instead of the default public Identity servers.
 matrix_synapse_trusted_third_party_id_servers: "{{ [matrix_server_fqn_matrix] if matrix_ma1sd_enabled else matrix_synapse_id_servers_public }}"
 
+# When ma1sd is enabled, we can use it to validate email addresses and phone numbers.
+# Synapse can validate email addresses by itself as well, but it's probably not what we want by default when we have an identity server.
+matrix_synapse_account_threepid_delegates_email: "{{ 'http://matrix-ma1sd:8090' if matrix_ma1sd_enabled else '' }}"
+matrix_synapse_account_threepid_delegates_msisdn: "{{ 'http://matrix-ma1sd:8090' if matrix_ma1sd_enabled else '' }}"
+
 # Normally, matrix-nginx-proxy is enabled and nginx can reach Synapse over the container network.
 # If matrix-nginx-proxy is not enabled, or you otherwise have a need for it,
 # you can expose Synapse's ports to the host.
diff --git a/roles/matrix-synapse/defaults/main.yml b/roles/matrix-synapse/defaults/main.yml
index f896f232..38cd2321 100644
--- a/roles/matrix-synapse/defaults/main.yml
+++ b/roles/matrix-synapse/defaults/main.yml
@@ -164,6 +164,14 @@ matrix_synapse_enable_group_creation: false
 # A list of 3PID types which users must supply when registering (possible values: email, msisdn).
 matrix_synapse_registrations_require_3pid: []
 
+# The server to use for email threepid validation. When empty, Synapse does it by itself.
+# Otherwise, this should be pointed to an identity server.
+matrix_synapse_account_threepid_delegates_email: ''
+
+# The server to use for phone number threepid validation. When empty, validation cannot happen, as Synapse doesn't support it.
+# To make it work, this should be pointed to an identity server.
+matrix_synapse_account_threepid_delegates_msisdn: ''
+
 # Users who register on this homeserver will automatically be joined to these rooms.
 # Rooms are to be specified using addresses (e.g. `#address:example.com`)
 matrix_synapse_auto_join_rooms: []
diff --git a/roles/matrix-synapse/templates/synapse/homeserver.yaml.j2 b/roles/matrix-synapse/templates/synapse/homeserver.yaml.j2
index b3adcac9..310421e9 100644
--- a/roles/matrix-synapse/templates/synapse/homeserver.yaml.j2
+++ b/roles/matrix-synapse/templates/synapse/homeserver.yaml.j2
@@ -1060,8 +1060,8 @@ trusted_third_party_id_servers:
 # If a delegate is specified, the config option public_baseurl must also be filled out.
 #
 account_threepid_delegates:
-    #email: https://example.com     # Delegate email sending to example.com
-    #msisdn: http://localhost:8090  # Delegate SMS sending to this local process
+    email: {{ matrix_synapse_account_threepid_delegates_email|to_json }}
+    msisdn: {{ matrix_synapse_account_threepid_delegates_msisdn|to_json }}
 
 # Users who register on this homeserver will automatically be joined
 # to these rooms