diff --git a/config/default.js b/config/default.js
index 912c909..4916bab 100644
--- a/config/default.js
+++ b/config/default.js
@@ -28,9 +28,9 @@ module.exports = {
   KAFKA_CLIENT_CERT_KEY: process.env.KAFKA_CLIENT_CERT_KEY ?
     process.env.KAFKA_CLIENT_CERT_KEY.replace('\\n', '\n') : null,
 
-  TC_API_V3_BASE_URL: process.env.TC_API_V3_BASE_URL || '',
+  TC_API_V3_BASE_URL: process.env.TC_API_V3_BASE_URL || 'http://api.topcoder-dev.com/v3',
   TC_API_V4_BASE_URL: process.env.TC_API_V4_BASE_URL || '',
-  TC_API_V5_BASE_URL: process.env.TC_API_V5_BASE_URL || '',
+  TC_API_V5_BASE_URL: process.env.TC_API_V5_BASE_URL || 'https://api.topcoder-dev.com/v5',
   API_CONTEXT_PATH: process.env.API_CONTEXT_PATH || '/v5/notifications',
   TC_API_BASE_URL: process.env.TC_API_BASE_URL || '',
 
@@ -135,7 +135,7 @@ module.exports = {
   // email notification service related variables
   ENV: process.env.ENV,
   ENABLE_EMAILS: process.env.ENABLE_EMAILS ? Boolean(process.env.ENABLE_EMAILS) : false,
-  ENABLE_DEV_MODE: process.env.ENABLE_DEV_MODE ? Boolean(process.env.ENABLE_DEV_MODE) : true,
+  ENABLE_DEV_MODE: process.env.ENABLE_DEV_MODE === 'true',
   DEV_MODE_EMAIL: process.env.DEV_MODE_EMAIL,
   DEFAULT_REPLY_EMAIL: process.env.DEFAULT_REPLY_EMAIL,
   ENABLE_HOOK_BULK_NOTIFICATION: process.env.ENABLE_HOOK_BULK_NOTIFICATION || false,
diff --git a/src/common/tcApiHelper.js b/src/common/tcApiHelper.js
index 0bd9ca5..8a030b7 100644
--- a/src/common/tcApiHelper.js
+++ b/src/common/tcApiHelper.js
@@ -88,6 +88,103 @@ function* getUsersByHandles(handles) {
   return yield searchUsersByQuery(query);
 }
 
+/**
+ * Get users by handles or userIds.
+ * @param {Array<Object>} handles the objects that has user handles.
+ * @param {Array<Object>} userIds the objects that has userIds.
+ * @returns {Array<Object>} the matched users
+ */
+function* getUsersByHandlesAndUserIds(handles, userIds) {
+  if ((!handles || handles.length === 0) && (!userIds || userIds.length === 0)) {
+    return [];
+  }
+  const handlesQuery = _.map(handles, h => `handleLower:${h.handle.toLowerCase()}`);
+  const userIdsQuery = _.map(userIds, u => `userId:${u.userId}`);
+  const query = _.concat(handlesQuery, userIdsQuery).join(URI.encodeQuery(' OR ', 'utf8'));
+  try {
+    return yield searchUsersByQuery(query);
+  } catch (err) {
+    const error = new Error(err.response.text);
+    error.status = err.status;
+    throw error;
+  }
+}
+
+/**
+ * Search users by query string.
+ * @param {String} query the query string
+ * @returns {Array} the matched users
+ */
+function* searchUsersByEmailQuery(query) {
+  const token = yield getM2MToken();
+  const res = yield request
+      .get(`${
+        config.TC_API_V3_BASE_URL
+        }/users?filter=${
+        query
+        }&fields=id,email,handle`)
+      .set('Authorization', `Bearer ${token}`);
+  if (!_.get(res, 'body.result.success')) {
+    throw new Error(`Failed to search users by query: ${query}`);
+  }
+  const records = _.get(res, 'body.result.content') || [];
+
+  logger.verbose(`Searched users: ${JSON.stringify(records, null, 4)}`);
+  return records;
+}
+
+/**
+ * Get users by emails.
+ * @param {Array<Object>} emails the objects that has user emails.
+ * @returns {Array<Object>} the matched users
+ */
+function* getUsersByEmails(emails) {
+  if (!emails || emails.length === 0) {
+    return [];
+  }
+  const users = [];
+  try {
+    for (const email of emails) {
+      const query = `email%3D${email.email}`;
+      const result = yield searchUsersByEmailQuery(query);
+      users.push(...result);
+    }
+    return users;
+  } catch (err) {
+    const error = new Error(err.response.text);
+    error.status = err.status;
+    throw error;
+  }
+}
+
+/**
+ * Get users by uuid.
+ * @param {Array<Object>} ids the objects that has user uuids.
+ * @returns {Array<Object>} the matched users
+ */
+function* getUsersByUserUUIDs(ids, enrich) {
+  if (!ids || ids.length === 0) {
+    return [];
+  }
+  const users = [];
+  const token = yield getM2MToken();
+  try {
+    for (const id of ids) {
+      const res = yield request
+      .get(`${config.TC_API_V5_BASE_URL}/users/${id.userUUID}${enrich ? '?enrich=true' : ''}`)
+      .set('Authorization', `Bearer ${token}`);
+      const user = res.body;
+      logger.verbose(`Searched users: ${JSON.stringify(user, null, 4)}`);
+      users.push(user);
+    }
+    return users;
+  } catch (err) {
+    const error = new Error(err.response.text);
+    error.status = err.status;
+    throw error;
+  }
+}
+
 /**
  * Send message to bus.
  * @param {Object} data the data to send
@@ -158,21 +255,30 @@ function* checkNotificationSetting(userId, notificationType, serviceId) {
 }
 
 /**
- * Notify user via email.
+ * Notify user via web.
  * @param {Object} message the Kafka message payload
- * @return {Object} notification details.
+ * @return {Array<Object>} notification details.
  */
 function* notifyUserViaWeb(message) {
   const notificationType = message.type;
-  const userId = message.details.userId;
-  // if web notification is explicitly disabled for current notification type do nothing
-  const allowed = yield checkNotificationSetting(userId, notificationType, constants.SETTINGS_WEB_SERVICE_ID);
-  if (!allowed) {
-    logger.verbose(`Notification '${notificationType}' won't be sent by '${constants.SETTINGS_WEB_SERVICE_ID}'`
+  const notifications = [];
+  for (const recipient of message.details.recipients) {
+    const userId = recipient.userId;
+    if (_.isUndefined(userId)) {
+      logger.error(`userId not received for user: ${JSON.stringify(recipient, null, 4)}`);
+      continue;
+    }
+    // if web notification is explicitly disabled for current notification type do nothing
+    const allowed = yield checkNotificationSetting(userId, notificationType, constants.SETTINGS_WEB_SERVICE_ID);
+    if (!allowed) {
+      logger.verbose(`Notification '${notificationType}' won't be sent by '${constants.SETTINGS_WEB_SERVICE_ID}'`
     + ` service to the userId '${userId}' due to his notification settings.`);
-    return;
+      continue;
+    }
+    notifications.push(_.assign({}, _.pick(message.details, ['contents', 'version']), { userId }));
   }
-  return message.details;
+
+  return notifications;
 }
 
 /**
@@ -182,15 +288,9 @@ function* notifyUserViaWeb(message) {
 function* notifyUserViaEmail(message) {
   const notificationType = message.type;
   const topic = constants.BUS_API_EVENT.EMAIL.UNIVERSAL;
+  const cc = _.map(_.filter(message.details.cc, c => !_.isUndefined(c.email)), 'email');
   for (const recipient of message.details.recipients) {
     const userId = recipient.userId;
-    // if email notification is explicitly disabled for current notification type do nothing
-    const allowed = yield checkNotificationSetting(userId, notificationType, constants.SETTINGS_EMAIL_SERVICE_ID);
-    if (!allowed) {
-      logger.verbose(`Notification '${notificationType}' won't be sent by '${constants.SETTINGS_EMAIL_SERVICE_ID}'`
-      + ` service to the userId '${userId}' due to his notification settings.`);
-      continue;
-    }
     let userEmail;
     // if dev mode for email is enabled then replace recipient email
     if (config.ENABLE_DEV_MODE) {
@@ -198,7 +298,17 @@ function* notifyUserViaEmail(message) {
     } else {
       userEmail = recipient.email;
       if (!userEmail) {
-        logger.error(`Email not received for user: ${userId}`);
+        logger.error(`Email not received for user: ${JSON.stringify(recipient, null, 4)}`);
+        continue;
+      }
+    }
+    // skip checking notification setting if userId is not found.
+    if (!_.isUndefined(userId)) {
+    // if email notification is explicitly disabled for current notification type do nothing
+      const allowed = yield checkNotificationSetting(userId, notificationType, constants.SETTINGS_EMAIL_SERVICE_ID);
+      if (!allowed) {
+        logger.verbose(`Notification '${notificationType}' won't be sent by '${constants.SETTINGS_EMAIL_SERVICE_ID}'`
+      + ` service to the userId '${userId}' due to his notification settings.`);
         continue;
       }
     }
@@ -206,7 +316,7 @@ function* notifyUserViaEmail(message) {
     const payload = {
       from: message.details.from,
       recipients,
-      cc: message.details.cc || [],
+      cc,
       data: message.details.data || {},
       sendgrid_template_id: message.details.sendgridTemplateId,
       version: message.details.version,
@@ -496,6 +606,9 @@ module.exports = {
   getM2MToken,
   getUsersBySkills,
   getUsersByHandles,
+  getUsersByHandlesAndUserIds,
+  getUsersByEmails,
+  getUsersByUserUUIDs,
   sendMessageToBus,
   notifySlackChannel,
   checkNotificationSetting,
diff --git a/src/services/UniversalNotificationService.js b/src/services/UniversalNotificationService.js
index 3f41d86..c03f896 100644
--- a/src/services/UniversalNotificationService.js
+++ b/src/services/UniversalNotificationService.js
@@ -3,7 +3,7 @@
  */
 
 'use strict';
-
+const _ = require('lodash');
 const joi = require('joi');
 const logger = require('../common/logger');
 const tcApiHelper = require('../common/tcApiHelper');
@@ -16,15 +16,19 @@ const emailSchema = joi.object().keys({
     from: joi.string().email().required(),
     recipients: joi.array().items(
       joi.object().keys({
-        userId: joi.number().integer().required(),
-        email: joi.string().email().required(),
-      }).required()
+        userId: joi.number().integer(),
+        userUUID: joi.string().uuid(),
+        email: joi.string().email(),
+        handle: joi.string(),
+      }).min(1).required()
     ).min(1).required(),
     cc: joi.array().items(
       joi.object().keys({
         userId: joi.number().integer(),
-        email: joi.string().email().required(),
-      }).required()
+        userUUID: joi.string().uuid(),
+        email: joi.string().email(),
+        handle: joi.string(),
+      }).min(1)
     ),
     data: joi.object().keys({
       subject: joi.string(),
@@ -48,7 +52,14 @@ const webSchema = joi.object().keys({
   serviceId: joi.string().valid(constants.SETTINGS_WEB_SERVICE_ID).required(),
   type: joi.string().required(),
   details: joi.object().keys({
-    userId: joi.number().integer().required(),
+    recipients: joi.array().items(
+      joi.object().keys({
+        userId: joi.number().integer(),
+        userUUID: joi.string().uuid(),
+        email: joi.string().email(),
+        handle: joi.string(),
+      }).min(1).required()
+    ).min(1).required(),
     contents: joi.object(),
     version: joi.number().integer().required(),
   }).required(),
@@ -63,6 +74,97 @@ function validator(data, schema) {
   return true;
 }
 
+
+/**
+ * Complete missing user fields of given payload details
+ * This function mutates the given details object.
+ * @param {Object} details the object which has recipients array
+ * @param {Boolean} findEmail true if emails are needed
+ * @param {Boolean} findUserId true if userIds are needed
+ * @returns {undefined}
+ */
+function* completeMissingFields(details, findEmail, findUserId) {
+  const getFieldsByUserId = [];
+  const getFieldsByHandle = [];
+  const getFieldsByUserUUID = [];
+  const getFieldsByEmail = [];
+  function findMissingFields(data, email, userId) {
+    for (const recipient of data) {
+      if (_.isUndefined(recipient.email) && email) {
+        if (!_.isUndefined(recipient.userId)) {
+          getFieldsByUserId.push(recipient);
+        } else if (!_.isUndefined(recipient.handle)) {
+          getFieldsByHandle.push(recipient);
+        } else {
+          getFieldsByUserUUID.push(recipient);
+        }
+      } else if (_.isUndefined(recipient.userId) && userId) {
+        if (!_.isUndefined(recipient.handle)) {
+          getFieldsByHandle.push(recipient);
+        } else if (!_.isUndefined(recipient.email)) {
+          getFieldsByEmail.push(recipient);
+        } else {
+          getFieldsByUserUUID.push(recipient);
+        }
+      }
+    }
+  }
+
+  findMissingFields(details.recipients, findEmail, findUserId);
+  if (_.isArray(details.cc) && !_.isEmpty(details.cc)) {
+    findMissingFields(details.cc, findEmail, false);
+  }
+  const foundUsersByHandleOrId = yield tcApiHelper.getUsersByHandlesAndUserIds(getFieldsByHandle, getFieldsByUserId);
+  if (!_.isEmpty(foundUsersByHandleOrId)) {
+    for (const user of [...getFieldsByUserId, ...getFieldsByHandle]) {
+      const found = _.find(foundUsersByHandleOrId, !_.isUndefined(user.handle)
+        ? ['handle', user.handle] : ['userId', user.userId]) || {};
+      if (!_.isUndefined(found.email) && _.isUndefined(user.email)) {
+        _.assign(user, { email: found.email });
+      }
+      if (!_.isUndefined(found.userId) && _.isUndefined(user.userId)) {
+        _.assign(user, { userId: found.userId });
+      }
+    }
+  }
+  const foundUsersByEmail = yield tcApiHelper.getUsersByEmails(getFieldsByEmail);
+  if (!_.isEmpty(foundUsersByEmail)) {
+    for (const user of getFieldsByEmail) {
+      const found = _.find(foundUsersByEmail, ['email', user.email]) || {};
+      if (!_.isUndefined(found.id)) {
+        _.assign(user, { userId: found.id });
+      }
+    }
+  }
+  const foundUsersByUUID = yield tcApiHelper.getUsersByUserUUIDs(getFieldsByUserUUID, true);
+  if (!_.isEmpty(foundUsersByUUID)) {
+    for (const user of getFieldsByUserUUID) {
+      const found = _.find(foundUsersByUUID, ['id', user.userUUID]) || {};
+      if (!_.isUndefined(found.externalProfiles) && !_.isEmpty(found.externalProfiles)) {
+        _.assign(user, { userId: _.toInteger(_.get(found.externalProfiles[0], 'externalId')) });
+      }
+      if (!_.isUndefined(found.handle) && _.isUndefined(user.handle)) {
+        _.assign(user, { handle: found.handle });
+      }
+    }
+
+    if (findEmail) {
+      const usersHaveId = _.filter(getFieldsByUserUUID, u => !_.isUndefined(u.userId));
+      const usersHaveHandle = _.filter(getFieldsByUserUUID, u => _.isUndefined(u.userId) && !_.isUndefined(u.handle));
+      const foundUser = yield tcApiHelper.getUsersByHandlesAndUserIds(usersHaveHandle, usersHaveId);
+      if (!_.isEmpty(foundUser)) {
+        for (const user of getFieldsByUserUUID) {
+          const found = _.find(foundUser, !_.isUndefined(user.handle)
+            ? ['handle', user.handle] : ['userId', user.userId]) || {};
+          if (!_.isUndefined(found.email)) {
+            _.assign(user, { email: found.email });
+          }
+        }
+      }
+    }
+  }
+}
+
 /**
  * Handle notification message
  * @param {Object} message the Kafka message
@@ -70,11 +172,13 @@ function validator(data, schema) {
  */
 function* handle(message) {
   const notifications = [];
-  for (const data of message.payload) {
+  for (const data of message.payload.notifications) {
     try {
       switch (data.serviceId) {
         case constants.SETTINGS_EMAIL_SERVICE_ID:
           if (validator(data, emailSchema)) {
+            // find missing emails and userIds
+            yield completeMissingFields(data.details, true, true);
             yield tcApiHelper.notifyUserViaEmail(data);
           }
           break;
@@ -85,9 +189,11 @@ function* handle(message) {
           break;
         case constants.SETTINGS_WEB_SERVICE_ID:
           if (validator(data, webSchema)) {
-            const notification = yield tcApiHelper.notifyUserViaWeb(data);
-            if (notification) {
-              notifications.push(notification);
+            // find missing userIds
+            yield completeMissingFields(data.details, false, true);
+            const _notifications = yield tcApiHelper.notifyUserViaWeb(data);
+            if (_notifications) {
+              notifications.push(..._notifications);
             }
           }
           break;
@@ -107,14 +213,16 @@ handle.schema = {
     originator: joi.string().required(),
     timestamp: joi.date().required(),
     'mime-type': joi.string().required(),
-    payload: joi.array().items(
-      joi.object().keys({
-        serviceId: joi.string().valid(
-          constants.SETTINGS_EMAIL_SERVICE_ID,
-          constants.SETTINGS_SLACK_SERVICE_ID,
-          constants.SETTINGS_WEB_SERVICE_ID).required(),
-      }).unknown()
-    ).min(1).required(),
+    payload: joi.object().keys({
+      notifications: joi.array().items(
+        joi.object().keys({
+          serviceId: joi.string().valid(
+            constants.SETTINGS_EMAIL_SERVICE_ID,
+            constants.SETTINGS_SLACK_SERVICE_ID,
+            constants.SETTINGS_WEB_SERVICE_ID).required(),
+        }).unknown()
+      ).min(1).required(),
+    }).required(),
   }).required(),
 };