PASS
Open DNS servers
OK. Your DNS servers do not announce that they are open DNS servers. Although there is a slight chance that they really are open DNS servers, this is very unlikely. Open DNS servers increase the chances that of cache poisoning, can degrade performance of your DNS, and can cause your DNS servers to be used in an attack (so it is good that your DNS servers do not appear to be open DNS servers).
PASS
Acceptance of NULL <> sender
OK: All of your mailservers accept mail from "<>". You are required (RFC1123 5.2.9) to receive this type of mail (which includes reject/bounce messages and return receipts).
PASS
Open relay test
OK: All of your mailservers appear to be closed to relaying. This is not a thorough check, you can get a thorough one here.
ns1.xlab-group.com OK: 550-85.3b.354a.static.theplanet.com (test.DNSreport.com) [74.53.59.133] is 550-currently not permitted to relay through this server. Perhaps you have not 550-logged into the pop/imap server in the last 30 minutes or do not have SMTP 550 Authentication turned on in your email client. <br />