diff --git a/src/util/Postie.js b/src/util/Postie.js
index 668408d..73c8f9e 100644
--- a/src/util/Postie.js
+++ b/src/util/Postie.js
@@ -5,28 +5,28 @@ class Postie {
 
   _getSubscribers(topic) {
     const subscribers = this._topics.get(topic);
-    if (typeof subscribers === 'undefined') {
+    if (subscribers === undefined) {
       throw new Error(`Topic:"${topic}" doesn't exist.`);
     }
     return subscribers;
   }
 
-  _getSubscriber(topic, address) {
+  _getInboxes(topic, address) {
     const subscribers = this._getSubscribers(topic);
-    const subscriber = subscribers.get(address);
-    if (typeof subscriber === 'undefined') {
-      throw new Error(`Subscriber on topic:"${topic}" at address:"${address}" doesn't exist.`);
+    const inboxes = subscribers.get(address);
+    if (inboxes === undefined) {
+      throw new Error(`Inbox on topic:"${topic}" at address:"${address}" doesn't exist.`);
     }
-    return subscriber;
+    return inboxes;
   }
 
   hasTopic(topic) {
-    return typeof this._topics.get(topic) !== 'undefined';
+    return this._topics.get(topic) !== undefined;
   }
 
   hasSubscriber(topic, address) {
     const subscribers = this._getSubscribers(topic);
-    return typeof subscribers.get(address) !== 'undefined';
+    return subscribers.get(address) !== undefined;
   }
 
   hasTopicAndSubscriber(topic, address) {
@@ -45,24 +45,29 @@ class Postie {
       throw new TypeError('Inbox  must be a function.');
     }
 
-    if (typeof this._topics.get(topic) === 'undefined') {
+    if (this._topics.has(topic) === false) {
       this._topics.set(topic, new Map());
     }
     const subscribers = this._topics.get(topic);
-    if (subscribers.get(address)) {
-      throw new Error(`Subscription on topic:"${topic}" at address:"${address}" already exist.`);
-    }
-    subscribers.set(address, inbox);
+
+    const inboxes = subscribers.get(address) ?? new Set();
+    inboxes.add(inbox);
+    subscribers.set(address, inboxes);
+
+    return () => this.unsubscribe(topic, address, inbox);
   }
 
-  unsubscribe(topic, address) {
+  unsubscribe(topic, address, inbox) {
     const subscribers = this._getSubscribers(topic);
-    if (subscribers.has(address)) {
-      subscribers.delete(address);
-    } else throw new Error(`Unable to unsubscribe. Subscriber on topic:"${topic}" at address:"${address}" doesn't exist`);
-    if (subscribers.size === 0) {
-      this._topics.delete(topic);
-    }
+    if (!subscribers) throw new Error(`Unable to unsubscribe. Topic: "${topic}" doesn't exist.`);
+
+    const inboxes = subscribers.get(address);
+    if (!inboxes) throw new Error(`Unable to unsubscribe. Subscriber on topic:"${topic}" at address:"${address}" doesn't exist`);
+
+    if (!inboxes.delete(inbox)) throw new Error('Unable to unsubscribe. Inbox doesn\'t exist');
+
+    if (inboxes.size === 0) subscribers.delete(address);
+    if (subscribers.size === 0) this._topics.delete(topic);
   }
 
   /**
@@ -71,20 +76,21 @@ class Postie {
    * @param {*} data - Data to deliver to subscriber
    */
   post(topic, address, data) {
-    const sendPost = (subscriber, addr) => {
-      if (typeof subscriber === 'undefined') {
+    const sendPost = (inboxes, addr) => {
+      if (inboxes === undefined) {
         throw new Error(`Unable to post on topic:"${topic}" at address:"${addr}". Subscriber doesn't exist.`);
       }
-      subscriber(data);
+      inboxes.forEach((inbox) => inbox(data));
     };
-    if (Array.isArray(address)) {
-      const subscribers = this._getSubscribers(topic);
-      address.forEach((addr) => {
-        sendPost(subscribers.get(addr), addr);
-      });
+
+    if (typeof address === 'string') {
+      sendPost(this._getInboxes(topic, address), address);
       return;
     }
-    sendPost(this._getSubscriber(topic, address), address);
+    const subscribers = this._getSubscribers(topic);
+    address.forEach((addr) => {
+      sendPost(subscribers.get(addr), addr);
+    });
   }
 }