DNS Query using DNSServiceQueryRecord for kDNSServiceType_MX one entry returned

I'm using DNSServiceQueryRecord to get kDNSServiceType_MX using following:

DNSServiceQueryRecord(&self->_sdRef,
                      kDNSServiceFlagsReturnIntermediates,
                      0,
                      srvNameCStr, //for example "google.com"
                      kDNSServiceType_MX,
                      kDNSServiceClass_IN,
                      QueryRecordCallback,
                      (__bridge void *)(self)
                      );

and call back is called but there is only one entry:

NSMutableData *         rrData;
dns_resource_record_t * rr;
uint8_t                 u8;
uint16_t                u16;
uint32_t                u32;

assert(rdata != NULL);
assert(rdlen < 65536);
rrData = [NSMutableData data];
assert(rrData != nil);

u8 = 0;
[rrData appendBytes:&u8 length:sizeof(u8)];
u16 = htons(kDNSServiceType_MX);
[rrData appendBytes:&u16 length:sizeof(u16)];
u16 = htons(kDNSServiceClass_IN);
[rrData appendBytes:&u16 length:sizeof(u16)];
u32 = htonl(666);
[rrData appendBytes:&u32 length:sizeof(u32)];
u16 = htons(rdlen);
[rrData appendBytes:&u16 length:sizeof(u16)];
[rrData appendBytes:rdata length:rdlen];

rr = dns_parse_resource_record([rrData bytes], (uint32_t) [rrData length]);
assert(rr != NULL);

if (rr != NULL)
{
    NSString *result = nil;
    result = [NSString stringWithCString:rr->data.MX->name encoding:NSASCIIStringEncoding];
    dns_free_resource_record(rr);
}

so this returns only one entry. How to get the list of MX? What am I doing wrong? Thanks in advance!