func (s *DNSServer) handleMXRequest(r *dns.Msg, m *dns.Msg) {
	m.Answer = make([]dns.RR, 0, 2)
	query := r.Question[0].Name

	if query[len(query)-1] == '.' {
		query = query[:len(query)-1]
	}

	for service := range s.queryServices(query) {
		rr := new(dns.MX)

		var ttl int
		if service.Ttl != -1 {
			ttl = service.Ttl
		} else {
			ttl = s.config.ttl
		}

		rr.Hdr = dns.RR_Header{
			Name:   r.Question[0].Name,
			Rrtype: dns.TypeMX,
			Class:  dns.ClassINET,
			Ttl:    uint32(ttl),
		}
		rr.Mx = r.Question[0].Name
		m.Answer = append(m.Answer, rr)
	}
}

// handleDnsMX writes a MX record pointing to s.host into m for host name.
func (s *server) handleDnsMX(name host, m *dns.Msg) {
	r := new(dns.MX)
	r.Hdr = dns.RR_Header{
		Name:   name.dns(),
		Rrtype: dns.TypeMX,
		Class:  dns.ClassINET,
		Ttl:    3600,
	}
	r.Preference = 10
	r.Mx = s.self.dns()
	m.Answer = make([]dns.RR, 1)
	m.Answer[0] = r
}

func answerMX(q *dns.Question, v *DNSValue) dns.RR {
	answer := new(dns.MX)
	answer.Header().Name = q.Name
	answer.Header().Rrtype = dns.TypeMX
	answer.Header().Class = dns.ClassINET
	answer.Preference = 50 // default if not defined
	priority, err := strconv.Atoi(v.Attr["priority"])
	if err == nil {
		answer.Preference = uint16(priority)
	}
	if target, ok := v.Attr["target"]; ok {
		answer.Mx = strings.TrimSuffix(target, ".") + "."
	} else if v.Value != "" { // allows for simplified setting
		answer.Mx = strings.TrimSuffix(v.Value, ".") + "."
	}
	return answer
}

func (s *DNSServer) makeServiceMX(n string, service *Service) dns.RR {
	rr := new(dns.MX)

	var ttl int
	if service.Ttl != -1 {
		ttl = service.Ttl
	} else {
		ttl = s.config.ttl
	}

	rr.Hdr = dns.RR_Header{
		Name:   n,
		Rrtype: dns.TypeMX,
		Class:  dns.ClassINET,
		Ttl:    uint32(ttl),
	}

	rr.Mx = n

	return rr
}

func TestRRsToMapStrsWithOPTRecord(t *testing.T) {
	o := new(mkdns.OPT)
	o.Hdr.Name = "." // MUST be the root zone, per definition.
	o.Hdr.Rrtype = mkdns.TypeOPT

	r := new(mkdns.MX)
	r.Hdr = mkdns.RR_Header{Name: "miek.nl.", Rrtype: mkdns.TypeMX,
		Class: mkdns.ClassINET, Ttl: 3600}
	r.Preference = 10
	r.Mx = "mx.miek.nl."

	// The OPT record is a psuedo-record so it doesn't become a real record
	// in our conversion, and there will be 1 entry instead of 2.
	mapStrs := rrsToMapStrs([]mkdns.RR{o, r})
	assert.Len(t, mapStrs, 1)

	mapStr := mapStrs[0]
	assert.Equal(t, "IN", mapStr["class"])
	assert.Equal(t, "MX", mapStr["type"])
	assert.Equal(t, "mx.miek.nl.", mapStr["data"])
	assert.Equal(t, "miek.nl.", mapStr["name"])
	assert.EqualValues(t, 10, mapStr["preference"])
}