code: func (s *WMailServer) Archive(env *whisper.Envelope) {
  	key := NewDbKey(env.Expiry-env.TTL, env.Hash())
  	rawEnvelope, err := rlp.EncodeToBytes(env)
  	if err != nil {
  		log.Error(fmt.Sprintf("rlp.EncodeToBytes failed: %s", err))
  	} else {
  		err = s.db.Put(key.raw, rawEnvelope, nil)
  		if err != nil {
  			log.Error(fmt.Sprintf("Writing to DB failed: %s", err))
  		}
  	}
  }
docs: // Archive stores the