diff --git a/src/db.ts b/src/db.ts
index bba4cb2..6873ade 100644
--- a/src/db.ts
+++ b/src/db.ts
@@ -7,7 +7,7 @@ import ChangelogModel from './models/changelog';
 // database urls, prod db url is retrieved automatically
 const TESTING_URL = 'mongodb://localhost/dfopdb_test';
 const DEV_URL = 'mongodb://localhost/dfopdb';
-const debugging = true;
+const debugging = false;
 
 if (process.env.NODE_ENV !== 'production' && debugging) {
   mongoose.set('debug', true);  // enable mongoose debug
@@ -19,7 +19,8 @@ export default class db {
     mode: null,
   };
 
-  static connect (mode = '', done: Function = () => {}) {  // set mode to test for unit/integration tests, otherwise skip parameters. done is also only needed for testing
+  // set mode to test for unit/integration tests, otherwise skip parameters. done is also only needed for testing
+  static connect (mode = '', done: Function = () => {}) {
     if (this.state.db) return done();  // db is already connected
 
     // find right connection url
@@ -43,9 +44,14 @@ export default class db {
     }
 
     // connect to db
-    mongoose.connect(connectionString, {useNewUrlParser: true, useUnifiedTopology: true, useCreateIndex: true, connectTimeoutMS: 10000}, err => {
+    mongoose.connect(connectionString, {
+      useNewUrlParser: true,
+      useUnifiedTopology: true,
+      useCreateIndex: true,
+      connectTimeoutMS: 10000
+    }, err => {
       if (err) done(err);
-    });
+    }).then(() => {});
     mongoose.connection.on('error', console.error.bind(console, 'connection error:'));
     mongoose.connection.on('connected', () => {  // evaluation connection behaviour on prod
       if (process.env.NODE_ENV !== 'test') {  // Do not interfere with testing
@@ -63,7 +69,7 @@ export default class db {
         mongoose.connection.close(() => {
           console.info('Mongoose default connection disconnected through app termination');
           process.exit(0);
-        });
+        }).then(() => {});
       }
     });
     mongoose.connection.once('open', () => {
@@ -79,14 +85,15 @@ export default class db {
       console.info(process.env.NODE_ENV === 'test' ? '' : `Disconnected from database`);
       this.state.db = 0;
       done();
-    });
+    }).then(() => {});
   }
 
   static getState () {
     return this.state;
   }
 
-  static drop (done: Function = () => {}) {  // drop all collections of connected db (only dev and test for safety reasons ;)
+  // drop all collections of connected db (only dev and test for safety reasons)
+  static drop (done: Function = () => {}) {
     if (!this.state.db || this.state.mode === 'prod') return done();  // no db connection or prod db
     this.state.db.db.listCollections().toArray((err, collections) => {  // get list of all collections
       if (collections.length === 0) {  // there are no collections to drop
@@ -106,7 +113,8 @@ export default class db {
   }
 
   static loadJson (json, done: Function = () => {}) {  // insert given JSON data into db, uses core mongodb methods
-    if (!this.state.db || !json.hasOwnProperty('collections') || json.collections.length === 0) {  // no db connection or nothing to load
+    // no db connection or nothing to load
+    if (!this.state.db || !json.hasOwnProperty('collections') || json.collections.length === 0) {
       return done();
     }
 
@@ -126,8 +134,8 @@ export default class db {
     });
   }
 
-  // changelog entry
-  static log(req, thisOrCollection, conditions = null, data = null) {  // expects (req, this (from query helper)) or (req, collection, conditions, data)
+  // changelog entry, expects (req, this (from query helper)) or (req, collection, conditions, data)
+  static log(req, thisOrCollection, conditions = null, data = null) {
     if (! (conditions || data)) {  // (req, this)
       data = thisOrCollection._update ? _.cloneDeep(thisOrCollection._update) : {};  // replace undefined with {}
       Object.keys(data).forEach(key => {
@@ -136,12 +144,24 @@ export default class db {
           delete data[key];
         }
       });
-      new ChangelogModel({action: req.method + ' ' + req.url, collectionName: thisOrCollection._collection.collectionName, conditions: thisOrCollection._conditions, data: data, user_id: req.authDetails.id ? req.authDetails.id : null}).save(err => {
+      new ChangelogModel({
+        action: req.method + ' ' + req.url,
+        collectionName: thisOrCollection._collection.collectionName,
+        conditions: thisOrCollection._conditions,
+        data: data,
+        user_id: req.authDetails.id ? req.authDetails.id : null
+      }).save(err => {
         if (err) console.error(err);
       });
     }
     else {  // (req, collection, conditions, data)
-      new ChangelogModel({action: req.method + ' ' + req.url, collectionName: thisOrCollection, conditions: conditions, data: data, user_id: req.authDetails.id ? req.authDetails.id : null}).save(err => {
+      new ChangelogModel({
+        action: req.method + ' ' + req.url,
+        collectionName: thisOrCollection,
+        conditions: conditions,
+        data: data,
+        user_id: req.authDetails.id ? req.authDetails.id : null
+      }).save(err => {
         if (err) console.error(err);
       });
     }
diff --git a/src/helpers/mail.ts b/src/helpers/mail.ts
index c8291d1..7f7e64d 100644
--- a/src/helpers/mail.ts
+++ b/src/helpers/mail.ts
@@ -10,7 +10,7 @@ export default class Mail{
   static mailPass: string;
 
   static init() {
-    this.mailPass = Array(64).map(() => Math.floor(Math.random() * 10)).join('');
+    this.mailPass = Array(64).fill(0).map(() => Math.floor(Math.random() * 10)).join('');
     this.uri = JSON.parse(process.env.VCAP_SERVICES).Mail[0].credentials.uri;
     this.auth.username = JSON.parse(process.env.VCAP_SERVICES).Mail[0].credentials.username;
     this.auth.password = JSON.parse(process.env.VCAP_SERVICES).Mail[0].credentials.password;
@@ -48,6 +48,7 @@ export default class Mail{
         auth: this.auth
       });
     }).then(() => {  // init done successfully
+      console.info('Mail service established successfully');
       this.send('lukas.veit@bosch.com', 'Mail Service started', new Date().toString());
     }).catch(err => {  // anywhere an error occurred
       console.error(`Mail init error: ${err.request.method} ${err.request.path}: ${err.response.status}`,
diff --git a/src/index.ts b/src/index.ts
index 54f3c68..7f3834f 100644
--- a/src/index.ts
+++ b/src/index.ts
@@ -6,6 +6,7 @@ import helmet from 'helmet';
 import cors from 'cors';
 import api from './api';
 import db from './db';
+import Mail from './helpers/mail';
 
 // TODO: check header, also in UI
 
@@ -17,9 +18,11 @@ console.info(process.env.NODE_ENV === 'production' ?
 // mongodb connection
 db.connect();
 
+// mail service
+Mail.init();
+
 // create Express app
 const app = express();
-app.disable('x-powered-by');
 
 // get port from environment, defaults to 3000
 const port = process.env.PORT || 3000;