Be explicit about mailserver routes

src/routes/mailserver.js

@@ -5,16 +5,14 @@ exports = module.exports = {
 };
 
 var addons = require('../addons.js'),
-    assert = require('assert'),
     BoxError = require('../boxerror.js'),
     middleware = require('../middleware/index.js'),
     HttpError = require('connect-lastmile').HttpError,
     url = require('url');
 
 function proxy(req, res, next) {
-    assert.strictEqual(typeof req.params.pathname, 'string');
-
     let parsedUrl = url.parse(req.url, true /* parseQueryString */);
+    const pathname = req.path.split('/').pop();
 
     // do not proxy protected values
     delete parsedUrl.query['access_token'];
@@ -25,7 +23,7 @@ function proxy(req, res, next) {
         if (error) return next(BoxError.toHttpError(error));
 
         parsedUrl.query['access_token'] = addonDetails.token;
-        req.url = url.format({ pathname: req.params.pathname, query: parsedUrl.query });
+        req.url = url.format({ pathname: pathname, query: parsedUrl.query });
 
         const proxyOptions = url.parse(`https://${addonDetails.ip}:3000`);
         proxyOptions.rejectUnauthorized = false;