diff --git a/app/javascript/dashboard/store/modules/contactConversations.js b/app/javascript/dashboard/store/modules/contactConversations.js
index 55dfcf441..0edced126 100644
--- a/app/javascript/dashboard/store/modules/contactConversations.js
+++ b/app/javascript/dashboard/store/modules/contactConversations.js
@@ -25,7 +25,9 @@ export const createConversationPayload = ({ params, contactId, files }) => {
   payload.append('inbox_id', inboxId);
   payload.append('contact_id', contactId);
   payload.append('source_id', sourceId);
-  payload.append('additional_attributes[mail_subject]', mailSubject);
+  if (mailSubject) {
+    payload.append('additional_attributes[mail_subject]', mailSubject);
+  }
   payload.append('assignee_id', assigneeId);
 
   return payload;
diff --git a/app/javascript/dashboard/store/modules/specs/contactConversations/actions.spec.js b/app/javascript/dashboard/store/modules/specs/contactConversations/actions.spec.js
index b403c0d4a..dd3b52587 100644
--- a/app/javascript/dashboard/store/modules/specs/contactConversations/actions.spec.js
+++ b/app/javascript/dashboard/store/modules/specs/contactConversations/actions.spec.js
@@ -282,6 +282,24 @@ describe('createConversationPayload', () => {
     expect(payload.get('assignee_id')).toBe(options.params.assigneeId);
     expect(payload.getAll('message[attachments][]')).toEqual([]);
   });
+
+  it('omits mail_subject when mailSubject is undefined', () => {
+    const options = {
+      params: {
+        inboxId: '1',
+        message: {
+          content: 'Test message content',
+        },
+        sourceId: '12',
+        assigneeId: '123',
+      },
+      contactId: '23',
+    };
+
+    const payload = createConversationPayload(options);
+
+    expect(payload.has('additional_attributes[mail_subject]')).toBe(false);
+  });
 });
 
 describe('createWhatsAppConversationPayload', () => {