thanks that helps. I would also like to know if system notifications can be disabled altogether

Hello,

You have to customize code.

Just create new module and write below code.

class hr_employee(osv.osv):

    _inherit = 'hr.employee'

    def _broadcast_welcome(self, cr, uid, employee_id, context=None):

        if not context: context={}

        context.update({'from_broadcast':True})

        return super(hr_employee,self)._broadcast_welcome(cr, uid, employee_id, context=context)

    @api.cr_uid_ids_context

    def message_post(self, cr, uid, thread_id, body='', subject=None, type='notification', subtype=None, parent_id=False,     attachments=None, context=None, **kwargs):

        if context.get('from_broadcast'):

            body = 'Your new message....................'

    return super(hr_employee, self).message_post(cr, uid, thread_id, body=body, subject=subject, type=type, subtype=subtype,     parent_id=parent_id, attachments=attachments, context=context, **kwargs)

May be this will useful you.

Thanks.

Shamji