diff --git a/.travis.yml b/.travis.yml
index e4d9c61..ce22855 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -1,9 +1,7 @@
 sudo: false
 language: node_js
 node_js:
-  - "4"
   - "6"
-  - "7"
 before_script:
   - npm install -g grunt-cli
   - mongo test_db --eval 'db.addUser("travis", "test");'
diff --git a/package.json b/package.json
index 6b999f7..82c2072 100644
--- a/package.json
+++ b/package.json
@@ -7,7 +7,7 @@
     "url": "https://github.com/mailvelope/keyserver.git"
   },
   "engines": {
-    "node": ">=4"
+    "node": ">=6"
   },
   "scripts": {
     "start": ": ${NODE_ENV=development} && node index.js",
diff --git a/src/dao/mongo.js b/src/dao/mongo.js
index 2416d16..6658729 100644
--- a/src/dao/mongo.js
+++ b/src/dao/mongo.js
@@ -31,9 +31,9 @@ class Mongo {
    * @param {String} pass   The database user's password
    * @yield {undefined}
    */
-  *init(options) {
-    let uri = 'mongodb://' + options.user + ':' + options.pass + '@' + options.uri;
-    this._db = yield MongoClient.connect(uri);
+  *init({ uri, user, pass }) {
+    let url = 'mongodb://' + user + ':' + pass + '@' + uri;
+    this._db = yield MongoClient.connect(url);
   }
 
   /**
diff --git a/src/email/email.js b/src/email/email.js
index f047c87..92f4b67 100644
--- a/src/email/email.js
+++ b/src/email/email.js
@@ -37,18 +37,18 @@ class Email {
    * @param {boolean} starttls   (optional) force STARTTLS to prevent downgrade attack. Defaults to true.
    * @param {boolean} pgp        (optional) if outgoing emails are encrypted to the user's public key.
    */
-  init(options) {
+  init({ host, port=465, auth, tls, starttls, pgp, sender }) {
     this._transport = nodemailer.createTransport({
-      host: options.host,
-      port: options.port || 465,
-      auth: options.auth,
-      secure: (options.tls !== undefined) ? util.isTrue(options.tls) : true,
-      requireTLS: (options.starttls !== undefined) ? util.isTrue(options.starttls) : true,
+      host,
+      port,
+      auth,
+      secure: (tls !== undefined) ? util.isTrue(tls) : true,
+      requireTLS: (starttls !== undefined) ? util.isTrue(starttls) : true,
     });
-    if (util.isTrue(options.pgp)) {
+    if (util.isTrue(pgp)) {
       this._transport.use('stream', openpgpEncrypt());
     }
-    this._sender = options.sender;
+    this._sender = sender;
   }
 
   /**
@@ -59,8 +59,7 @@ class Email {
    * @param {Object} origin     origin of the server
    * @yield {Object}            send response from the SMTP server
    */
-  *send(options) {
-    let template = options.template, userId = options.userId, keyId = options.keyId, origin = options.origin;
+  *send({ template, userId, keyId, origin }) {
     let message = {
       from: this._sender,
       to: userId,
@@ -87,26 +86,25 @@ class Email {
    * @param {Object} params    (optional) nodermailer template parameters
    * @yield {Object}           reponse object containing SMTP info
    */
-  *_sendHelper(options) {
+  *_sendHelper({ from, to, subject, text, html, params={} }) {
     let template = {
-      subject: options.subject,
-      text: options.text,
-      html: options.html,
-      encryptionKeys: [options.to.publicKeyArmored]
+      subject,
+      text,
+      html,
+      encryptionKeys: [to.publicKeyArmored]
     };
     let sender = {
       from: {
-        name: options.from.name,
-        address: options.from.email
+        name: from.name,
+        address: from.email
       }
     };
     let recipient = {
       to: {
-        name: options.to.name,
-        address: options.to.email
+        name: to.name,
+        address: to.email
       }
     };
-    let params = options.params || {};
 
     try {
       let sendFn = this._transport.templateSender(template, sender);
@@ -116,7 +114,7 @@ class Email {
       }
       return info;
     } catch(error) {
-      log.error('email', 'Sending message failed.', error, options);
+      log.error('email', 'Sending message failed.', error);
       util.throw(500, 'Sending email to user failed');
     }
   }
diff --git a/src/service/public-key.js b/src/service/public-key.js
index 64b45f8..f2d9a93 100644
--- a/src/service/public-key.js
+++ b/src/service/public-key.js
@@ -66,9 +66,8 @@ class PublicKey {
    * @param {Object} origin             Required for links to the keyserver e.g. { protocol:'https', host:'openpgpkeys@example.com' }
    * @yield {undefined}
    */
-  *put(options) {
+  *put({ publicKeyArmored, primaryEmail, origin }) {
     // parse key block
-    let publicKeyArmored = options.publicKeyArmored, primaryEmail = options.primaryEmail, origin = options.origin;
     let key = this._pgp.parseKey(publicKeyArmored);
     // check for existing verfied key by id or email addresses
     let verified = yield this.getVerified(key);
@@ -128,8 +127,7 @@ class PublicKey {
    * @param {string} nonce   The verification nonce proving email address ownership
    * @yield {undefined}
    */
-  *verify(options) {
-    let keyId = options.keyId, nonce = options.nonce;
+  *verify({ keyId, nonce }) {
     // look for verification nonce in database
     let query = { keyId, 'userIds.nonce':nonce };
     let key = yield this._mongo.get(query, DB_TYPE);
@@ -157,8 +155,7 @@ class PublicKey {
    * @param {string} keyId         (optional) The public key id
    * @yield {Object}               The verified key document
    */
-  *getVerified(options) {
-    let fingerprint = options.fingerprint, userIds = options.userIds, keyId = options.keyId;
+  *getVerified({ userIds, fingerprint, keyId }) {
     let queries = [];
     // query by fingerprint
     if (fingerprint) {
@@ -196,8 +193,7 @@ class PublicKey {
    * @param {String} email         (optional) The user's email address
    * @yield {Object}               The public key document
    */
-  *get(options) {
-    let fingerprint = options.fingerprint, keyId = options.keyId, email = options.email;
+  *get({ fingerprint, keyId, email }) {
     // look for verified key
     let userIds = email ? [{ email:email }] : undefined;
     let key = yield this.getVerified({ keyId, fingerprint, userIds });
@@ -224,8 +220,7 @@ class PublicKey {
    * @param {Object} origin   Required for links to the keyserver e.g. { protocol:'https', host:'openpgpkeys@example.com' }
    * @yield {undefined}
    */
-  *requestRemove(options) {
-    let keyId = options.keyId, email = options.email, origin = options.origin;
+  *requestRemove({ keyId, email, origin }) {
     // flag user ids for removal
     let key = yield this._flagForRemove(keyId, email);
     if (!key) {
@@ -277,8 +272,7 @@ class PublicKey {
    * @param {string} nonce   The verification nonce proving email address ownership
    * @yield {undefined}
    */
-  *verifyRemove(options) {
-    let keyId = options.keyId, nonce = options.nonce;
+  *verifyRemove({ keyId, nonce }) {
     // check if key exists in database
     let flagged = yield this._mongo.get({ keyId, 'userIds.nonce':nonce }, DB_TYPE);
     if (!flagged) {