Move MailError to BoxError

src/mailer.js

@@ -25,6 +25,7 @@ exports = module.exports = {
 };
 
 var assert = require('assert'),
+    BoxError = require('./boxerror.js'),
     constants = require('./constants.js'),
     custom = require('./custom.js'),
     debug = require('debug')('box:mailer'),
@@ -93,7 +94,7 @@ function sendMail(mailOptions, callback) {
         }));
 
         transport.sendMail(mailOptions, function (error) {
-            if (error) return callback(error);
+            if (error) return callback(new BoxError(BoxError.EXTERNAL_ERROR, error));
 
             debug(`Email "${mailOptions.subject}" sent to ${mailOptions.to}`);