[IMP] ecommerce: add instructions to enable deferred confirmation emails

The page title is renamed  "Performance management" to fit its new,
multipurpose content.

task-3872792

closes #12385

X-original-commit: b0cc1ee
Signed-off-by: Audrey Vandromme (auva) <[email protected]>
Signed-off-by: Antoine Vandevenne (anv) <[email protected]>

Author: AntoineVDV

content/applications/websites/ecommerce/ecommerce_management/performance.rst

@@ -1,5 +1,5 @@
 ======================
-Performance monitoring
+Performance management
 ======================
 
 Odoo integrates a variety of tools to analyze and improve the performance of your eCommerce
@@ -32,3 +32,29 @@ Analytics
 
 It is possible to link your Odoo website with :ref:`analytics/plausible` and
 :ref:`analytics/google-analytics`.
+
+.. _ecommerce/performance/email_queue:
+
+Email queue optimization
+========================
+
+For websites handling flash sales (e.g., event ticket sales) or experiencing high traffic spikes,
+order confirmation emails can become a performance bottleneck, potentially slowing down the checkout
+process for other customers.
+
+To improve performance, these emails can be queued and processed separately from the order
+confirmation flow. This is managed by the :guilabel:`Sales: Send pending emails` scheduled action,
+which sends queued emails as soon as possible.
+
+To enable asynchronous email sending:
+
+#. Enable the :doc:`developer mode </applications/general/developer_mode>`.
+#. Go to :menuselection:`Settings --> Technical --> System Parameters` and set the
+   :guilabel:`sale.async_emails` system parameter to `True`.
+#. Go to :menuselection:`Settings --> Technical --> Scheduled Actions` and enable the
+   :guilabel:`Sales: Send pending emails` scheduled action.
+
+.. caution::
+   Enabling this feature may delay order confirmation and invoice emails by a few minutes. It is
+   recommended only for high-traffic websites, as it can introduce unnecessary delays for e-commerce
+   websites with moderate traffic.