diff --git a/addons/mail/static/src/core/thread_service.js b/addons/mail/static/src/core/thread_service.js
index 813f494f324..2a8d4184383 100644
--- a/addons/mail/static/src/core/thread_service.js
+++ b/addons/mail/static/src/core/thread_service.js
@@ -681,6 +681,7 @@ export class ThreadService {
         const tmpId = lastMessageId + 0.01;
         const params = {
             context: {
+                mail_post_autofollow: !isNote && thread.hasWriteAccess,
                 temporary_id: tmpId,
             },
             post_data: {
diff --git a/addons/mail/static/tests/composer/suggested_recipients_test.js b/addons/mail/static/tests/composer/suggested_recipients_test.js
index 28b58aedab4..73721df62c8 100644
--- a/addons/mail/static/tests/composer/suggested_recipients_test.js
+++ b/addons/mail/static/tests/composer/suggested_recipients_test.js
@@ -206,6 +206,26 @@ QUnit.test(
     }
 );
 
+QUnit.test(
+    "suggested recipients should be added as follower when posting a message",
+    async (assert) => {
+        const pyEnv = await startServer();
+        const partnerId = pyEnv["res.partner"].create({
+            display_name: "John Jane",
+            email: "john@jane.be",
+        });
+        const fakeId = pyEnv["res.fake"].create({ partner_ids: [partnerId] });
+        const { openFormView } = await start({
+            serverData: { views },
+        });
+        await openFormView("res.fake", fakeId);
+        await click("button:contains(Send message)");
+        await insertText(".o-mail-Composer-input", "Dummy Message");
+        await click(".o-mail-Composer-send");
+        assert.strictEqual($(".o-mail-Followers-counter").text(), "1");
+    }
+);
+
 QUnit.test(
     "suggested recipient without partner are unchecked when closing the dialog without creating partner",
     async (assert) => {
diff --git a/addons/mail/static/tests/helpers/mock_server/controllers/discuss.js b/addons/mail/static/tests/helpers/mock_server/controllers/discuss.js
index f3e5d27c484..4387dd8a545 100644
--- a/addons/mail/static/tests/helpers/mock_server/controllers/discuss.js
+++ b/addons/mail/static/tests/helpers/mock_server/controllers/discuss.js
@@ -448,7 +448,7 @@ patch(MockServer.prototype, "mail/controllers/discuss", {
             res["hasReadAccess"] = false;
             return res;
         }
-        res['canPostOnReadonly'] = thread_model === 'mail.channel'; // model that have attr _mail_post_access='read'
+        res["canPostOnReadonly"] = thread_model === "mail.channel"; // model that have attr _mail_post_access='read'
         if (request_list.includes("activities")) {
             const activities = this.pyEnv["mail.activity"].searchRead([
                 ["id", "in", thread.activity_ids || []],
diff --git a/addons/mail/static/tests/helpers/mock_server/models/mail_thread.js b/addons/mail/static/tests/helpers/mock_server/models/mail_thread.js
index ba22e2c5946..abc8d11a868 100644
--- a/addons/mail/static/tests/helpers/mock_server/models/mail_thread.js
+++ b/addons/mail/static/tests/helpers/mock_server/models/mail_thread.js
@@ -154,6 +154,9 @@ patch(MockServer.prototype, "mail/models/mail_thread", {
      */
     _mockMailThreadMessagePost(model, ids, kwargs, context) {
         const id = ids[0]; // ensure_one
+        if (context?.["mail_post_autofollow"] && kwargs["partner_ids"].length > 0) {
+            this._mockMailThreadMessageSubscribe(model, ids, kwargs["partner_ids"]);
+        }
         if (kwargs.attachment_ids) {
             const attachments = this.getRecords("ir.attachment", [
                 ["id", "in", kwargs.attachment_ids],
@@ -197,7 +200,7 @@ patch(MockServer.prototype, "mail/models/mail_thread", {
      * @param {string} model not in server method but necessary for thread mock
      * @param {integer[]} ids
      * @param {integer[]} partner_ids
-     * @param {integer[]} subtype_ids
+     * @param {integer[]} [subtype_ids]
      * @returns {boolean}
      */
     _mockMailThreadMessageSubscribe(model, ids, partner_ids, subtype_ids) {
@@ -207,6 +210,14 @@ patch(MockServer.prototype, "mail/models/mail_thread", {
                     ["partner_id", "=", partner_id],
                 ])[0];
                 if (!followerId) {
+                    if (!subtype_ids || subtype_ids.length === 0) {
+                        subtype_ids = this.pyEnv["mail.message.subtype"].search([
+                            ["default", "=", true],
+                            "|",
+                            ["res_model", "=", model],
+                            ["res_model", "=", false],
+                        ]);
+                    }
                     followerId = this.pyEnv["mail.followers"].create({
                         is_active: true,
                         partner_id,
@@ -215,6 +226,9 @@ patch(MockServer.prototype, "mail/models/mail_thread", {
                         subtype_ids: subtype_ids,
                     });
                 }
+                this.pyEnv[model].write(ids, {
+                    message_follower_ids: [followerId],
+                });
                 this.pyEnv["res.partner"].write([partner_id], {
                     message_follower_ids: [followerId],
                 });
diff --git a/addons/mail/static/tests/helpers/model_definitions_setup.js b/addons/mail/static/tests/helpers/model_definitions_setup.js
index ffa14f68168..4cfe51defc1 100644
--- a/addons/mail/static/tests/helpers/model_definitions_setup.js
+++ b/addons/mail/static/tests/helpers/model_definitions_setup.js
@@ -95,6 +95,7 @@ insertModelFields("mail.message", {
     res_model_name: { string: "Res Model Name", type: "char" },
 });
 insertModelFields("mail.message.subtype", {
+    default: { default: true },
     subtype_xmlid: { type: "char" },
 });
 insertModelFields("mail.tracking.value", {