Fix allow_mail_archived_partner causing system notifications to send emails

allow_mail_archived_partner/models/mail_compose_message.py

@@ -0,0 +1,48 @@
+from odoo import models
+
+
+class MailComposeMessage(models.TransientModel):
+    _inherit = "mail.compose.message"
+
+    def _get_default_recipients(self):
+        """
+        This is the ONLY place that fills the 'To' field in Odoo 16.
+        We explicitly allow archived partners here for user-initiated sends.
+        """
+        recipients = super()._get_default_recipients()
+
+        model = self.env.context.get("active_model")
+        active_ids = self.env.context.get("active_ids") or []
+
+        if model == "account.move" and active_ids:
+            moves = self.env["account.move"].with_context(
+                active_test=False
+            ).browse(active_ids)
+
+            partners = moves.mapped("partner_id").filtered(
+                lambda p: p.email
+            )
+
+            if partners:
+                recipients["partner_ids"] = [(6, 0, partners.ids)]
+                recipients["email_to"] = ", ".join(partners.mapped("email"))
+
+        return recipients
+
+    def _prepare_mail_values(self, res_ids):
+        """
+        Explicit user send → allow archived partners internally.
+        """
+        model = self.env.context.get("active_model") or self.model
+
+        if model in ["sale.order", "account.move"]:
+            return super(
+                MailComposeMessage,
+                self.with_context(
+                    active_test=False,
+                    include_archived_partners=True,
+                    mail_notify_force=True,
+                )
+            )._prepare_mail_values(res_ids)
+
+        return super()._prepare_mail_values(res_ids)