Encountering the message Non-Authoritative Answer

Hello,

I am encountering an issue with SMTP on a MS Windows Server 2003 R2 Enterprise Edition server where some of the emails remain stuck in the c:\inetpub\mailroot\queue directory.

When I issue the nslookup command for on one of the domain names that's experiencing this problem from the command line I get the following results:
C:\>nslookup gmail.com
Server:  dns-rs1
Address:  12.127.17.71
Non-authoritative answer:
Name:    gmail.com
Addresses:  74.125.127.83, 74.125.79.83, 209.85.225.83
C:\>

I issued the same command for my domain name and received a similar result:
C:\>nslookup positivecoach.org
Server:  dns-rs1
Address:  12.127.17.71
Non-authoritative answer:
Name:    positivecoach.org
Address:  68.142.234.143

Can someone explain to me what Non-authoritative answer means?

Thank you in advance for your help.

Derek