diff --git a/docs/manual/output/email-output.rst b/docs/manual/output/email-output.rst
index c10e3756..8828bcbd 100644
--- a/docs/manual/output/email-output.rst
+++ b/docs/manual/output/email-output.rst
@@ -10,6 +10,19 @@ There are currently three types of email alerts:
 * Granular Notifications to any number of E-mail addresses
 * Daily E-mail Reports 
 
+.. warning::
+
+   **Consumer and hosted SMTP providers** (Gmail, Outlook.com, Yahoo, and similar)
+   generally do **not** allow unauthenticated relay from arbitrary servers. OSSEC sends
+   plain SMTP by default unless you configure authenticated mail (see
+   :ref:`manual-out-smtp-auth`). For Gmail you typically need an app password, OAuth,
+   or a relay service — not a bare ``smtp_server`` pointing at ``smtp.gmail.com``.
+
+   **Microsoft 365 / Exchange Online** requires authenticated SMTP or a connector;
+   see `Microsoft's SMTP setup guide
+   <https://support.microsoft.com/en-us/office/how-to-set-up-a-multifunction-device-or-application-to-send-email-using-microsoft-365-or-office-365-69f58e99-c550-4274-ad18-c805d654b4c4>`_.
+   Use :ref:`manual-out-smtp-auth` when your provider requires TLS and credentials.
+
 .. warning:: 
 
     Single E-Mail Notification must be setup before Granular Notification