dig nssearch minor mystery

[M. Meadows]

Just wondering why dig with nssearch and "@<ip>" produced two different answers when I ran it today. 
I assume the @8.8.8.8 (in the example below) isn't actually happening ... or it happened in one test and not the other. 
The results below were exactly as I saw them in the order that they are listed. 
I do know that the parent domain (lgusa.com) is not delegating email.lgusa.com based on other output from"dig any email.lgusa.com @ns11.worldnic.com".
I'm hoping, though, to get a better understanding of how nssearch is working in this example:
 
: dig lgusa.com +nssearch @8.8.8.8
SOA NS11.WORLDNIC.COM. namehost.WORLDNIC.COM. 108022419 10800 3600 604800 3600 from server ns11.worldnic.com in 28 ms.
SOA NS11.WORLDNIC.COM. namehost.WORLDNIC.COM. 108022419 10800 3600 604800 3600 from server ns12.worldnic.com in 39 ms.
 
: dig email.lgusa.com +nssearch @8.8.8.8
 
: dig email.lgusa.com +nssearch
SOA ns1.exacttarget.com. hostmaster.exacttarget.com. 2011112800 7200 3600 1209600 3600 from server ns1.exacttarget.com in 1 ms.
SOA ns1.exacttarget.com. hostmaster.exacttarget.com. 2011112800 7200 3600 1209600 3600 from server ns2.exacttarget.com in 93 ms.

: dig email.lgusa.com +nssearch @8.8.8.8
SOA ns1.exacttarget.com. hostmaster.exacttarget.com. 2011112800 7200 3600 1209600 3600 from server ns1.exacttarget.com in 5 ms.
SOA ns1.exacttarget.com. hostmaster.exacttarget.com. 2011112800 7200 3600 1209600 3600 from server ns2.exacttarget.com in 97 ms.

 Thanks very much!
 Marty
 

 		 	   		  
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