i18n

resource/locales/en-US/translation.json

@@ -698,7 +698,8 @@
     "administrator_menu":"Administrator Menu",
     "cannot_remove":"You cannot remove yourself from administrator",
     "cannot_invite_maximum_users": "Can not invite more than the maximum number of users.",
-    "current_users": "Current users:"
+    "current_users": "Current users:",
+    "valid_email": "Valid email address is required"
   },
 
   "user_group_management": {

resource/locales/ja/translation.json

@@ -681,7 +681,8 @@
     "administrator_menu": "管理者メニュー",
     "cannot_remove": "自分自身を管理者から外すことはできません",
     "cannot_invite_maximum_users": "ユーザーが上限に達したため招待できません。",
-    "current_users": "現在のユーザー数："
+    "current_users": "現在のユーザー数：",
+    "valid_email": "メールアドレスを入力してください。"
   },
 
   "user_group_management": {

src/client/js/components/Admin/Users/UserInviteModal.jsx

@@ -68,7 +68,7 @@ class UserInviteModal extends React.Component {
             value={this.state.email}
             onChange={this.handleInput}
           />
-          {!this.validEmail() && <p className="m-2 text-danger">Valid email address is required</p>}
+          {!this.validEmail() && <p className="m-2 text-danger">{ t('user_management.valid_email') }</p>}
         </Modal.Body>
         <Modal.Footer className="d-flex">
           <label className="mr-3 text-left" style={{ flex: 1 }}>