Hostweb list task email notification is not working

I developed an sharepoint hosted app, within the app, I managed to create a list named Application Form on Hosted Web, not in app web.

    var listCreationInfo = new SP.ListCreationInformation();
    listCreationInfo.set_title(_applicationList);
    listCreationInfo.set_templateType(SP.ListTemplateType.genericList);
    this.oList = hostWeb.get_lists().add(listCreationInfo);

Then I created an sharepoint 2010 approval workflow to Application Form.

I can receive workflow status email like:

Approval started on 19720116.

Approval (5) has completed on 20110501.

BUT I am not able to receive any task email notifications from the workflow.

If I create a list from SharePoint site directly, everything is working fine.

Any ideas?

Seraph Chen, SharePoint 2010 & Office 365, MCPD MCITP MCDBA