I have NIS version 18.5.0.125. (I think this is 2011)
I have been having a problem where emails that I am sending out generate an error in NIS and I have to resend. I discovered that I could turn off the outbound email scan and that seems to fix the problem. That is until NIS turns it back on...Even when I set the change to be permanent, it doesn't stick for more than a day or so.
Can you please tell us what this error is and possibly take a screen shot of it ? You can post it using the little tree located 3 icons away from the smilie. Thanks.