Standard format for MX?

Question

Hi, I have the following function:
public void testDnsLookup() throws Exception {
         Hashtable env = new Hashtable();
         env.put("java.naming.factory.initial",
                 "com.sun.jndi.dns.DnsContextFactory");
         DirContext ictx = new InitialDirContext( env );
         Attributes attrs =
            ictx.getAttributes( "hotmail.com", new String[] { "MX" });
         Attribute attr = attrs.get("MX");
         if (null != attr) {
              System.out.println(attr);
              NamingEnumeration<?> ne = attr.getAll();
              while(ne.hasMoreElements()) {
                   System.out.println(ne.nextElement());
     }Which prints out the following for hotmail:
MX: 5 mx3.hotmail.com., 5 mx4.hotmail.com., 5 mx1.hotmail.com., 5 mx2.hotmail.com.
5 mx3.hotmail.com.
5 mx4.hotmail.com.
5 mx1.hotmail.com.
5 mx2.hotmail.com.
My question is about the format of
5 mx2.hotmail.com.
Is this a standard format? What does the number in the front mean? Especially, is there always a number in the front?
Thanks.
M.

Answer 1

Found the answer. The number in the front represent the priority. Lower is better.
M.