The following is a bit saver:
var str = "/ucwa/oauth/v1/applications/101507538841/people/adan.maddox@dc.com/presence";
var n = str.match(/[^\/]*@[^\/]*/);
This way, the pattern of your email address doesn't really matter too much and you don't have to worry about the position of the email address in your string...
This probably matches best to your pattern.
If you want to extract more than one email addresses out of your pattern you could even go for:
var n = str.match(/[^\/]*@[^\/]*/g);
So, even the weird address mentioned before:
var str = 'ucwa/oauth/v1/applications/101507538841/\"very\".unusual"@strange.example.com/people/adan.maddox@dc.com'
Would bring you an array:
[""very".unusual"@strange.example.com", "adan.maddox@dc.com"]
See: http://jsfiddle.net/SnZxP/2/