Updated subscription-mail-helper.js - Don't wait for mailer to finish.

Note: When using encryptionKeys, confirmation redirects feel a bit
sluggish. This could probably be 'improved' by calling sendMail via
setTimout or fixed by moving sendMail to a worker.

lib/subscription-mail-helpers.js

@@ -144,11 +144,11 @@ function sendMail(list, email, template, subject, relativeUrls, mailOpts, subscr
                 }, err => {
                     if (err) {
                         log.error('Subscription', err);
-                        return callback(err);
                     }
-                    callback();
                 });
 
+                callback();
+
             });
         });
     });