The screenshot is a bit noisy
Via :-
<Options>
<Norton AntiVirus>
<Email>
'Untick' --- Scan outgoing Email box.
Click on <OK>, at this point the 'Protection Alert' box opens (If our NAVs are similar),
It allows, via a drop down menu, selection of your 'non scanning time period' twixt 15 mins and Permanently
My NAV version 11.0.16.4 From within Norton SystemWorks 2005 Version: 8.03
Works as expected on my machine.
Mind you I do tend to 'Ok' choices and not just close window !
Try the (Very elusive) Symantec knowledge base articles here :- http://search.symantec.com/custom/us/query.html
Enter the following in the 'Search' box
Scan Email
Under You may refine your search by selecting from the following options
Tick 'Knowledge Base' .... Hit the 'Search' button ..