advise users against using their emails as their username

customize.dist/credential.js

@@ -8,6 +8,12 @@ define([
     Cred.MINIMUM_PASSWORD_LENGTH = typeof(AppConfig.minimumPasswordLength) === 'number'?
         AppConfig.minimumPasswordLength: 8;
 
+    // https://stackoverflow.com/questions/46155/how-to-validate-an-email-address-in-javascript
+    Cred.isEmail = function (email) {
+        var re = /^(([^<>()\[\]\\.,;:\s@"]+(\.[^<>()\[\]\\.,;:\s@"]+)*)|(".+"))@((\[[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\])|(([a-zA-Z\-0-9]+\.)+[a-zA-Z]{2,}))$/;
+        return re.test(String(email).toLowerCase());
+    };
+
     Cred.isLongEnoughPassword = function (passwd) {
         return passwd.length >= Cred.MINIMUM_PASSWORD_LENGTH;
     };

www/common/translations/messages.json

@@ -436,6 +436,10 @@
     "register_cancel": "Go back",
     "register_warning": "Zero Knowledge means that we can't recover your data if you lose your password.",
     "register_alreadyRegistered": "This user already exists, do you want to log in?",
+    "register_emailWarning0": "It looks like you submitted your email as your username.",
+    "register_emailWarning1": "You can do that if you want, but it won't be sent to our server.",
+    "register_emailWarning2": "You won't be able to reset your password using your email as you can with many other services.",
+    "register_emailWarning3": "If you understand and would like to use your email for your username anyway, click OK.",
     "settings_cat_account": "Account",
     "settings_cat_drive": "CryptDrive",
     "settings_cat_cursor": "Cursor",

www/register/main.js

@@ -54,7 +54,9 @@ define([
         var registering = false;
         var test;
 
-        $register.click(function () {
+        var I_REALLY_WANT_TO_USE_MY_EMAIL_FOR_MY_USERNAME = false;
+
+        var registerClick = function () {
             var uname = $uname.val();
             var passwd = $passwd.val();
             var confirmPassword = $confirm.val();
@@ -62,6 +64,23 @@ define([
             var shouldImport = $checkImport[0].checked;
             var doesAccept = $checkAcceptTerms[0].checked;
 
+            if (Cred.isEmail(uname) && !I_REALLY_WANT_TO_USE_MY_EMAIL_FOR_MY_USERNAME) {
+                var warning = [
+                    Messages.register_emailWarning0,
+                    Messages.register_emailWarning1,
+                    Messages.register_emailWarning2,
+                    Messages.register_emailWarning3,
+                ].join('<br><br>');
+
+                Feedback.send("EMAIL_USERNAME_WARNING", true);
+
+                return void UI.confirm(warning, function (yes) {
+                    if (!yes) { return; }
+                    I_REALLY_WANT_TO_USE_MY_EMAIL_FOR_MY_USERNAME = true;
+                    registerClick();
+                }, {}, true);
+            }
+
             /* basic validation */
             if (!Cred.isLongEnoughPassword(passwd)) {
                 var warning = Messages._getKey('register_passwordTooShort', [
@@ -104,7 +123,9 @@ define([
                 },
             }, true);
             }, 150);
-        });
+        };
+
+        $register.click(registerClick);
 
         var clickRegister = Util.notAgainForAnother(function () {
             $register.click();