<prompt> Translate the following text to SwahiliFor a number of years, some mailers have pursued the idea of establishing customized postal rates andor terms of service through negotiation with the Postal Service.  <response>: Kwa miaka kadhaa, baadhi ya mailers wamekuwa kufuatilia wazo la kuanzisha maalum posta viwango na au masharti ya huduma kwa njia ya mazungumzo na Huduma ya Posta. 