diff --git a/src/constants.js b/src/constants.ts
similarity index 80%
rename from src/constants.js
rename to src/constants.ts
index 0d19f86..0bedd28 100644
--- a/src/constants.js
+++ b/src/constants.ts
@@ -1,3 +1,7 @@
+enum Topics {
+  CONTACT_DISCOVERY_TOPIC = '0xf8946aac'
+}
+
 module.exports = {
   post: {
     POW_TIME: 1,
@@ -12,10 +16,10 @@ module.exports = {
     message: "~#c4",
     chatRequest: "~#c2"
   },
-  topics: {
-    CONTACT_DISCOVERY_TOPIC: '0xf8946aac'
-  },
+  topics: Topics,
   regExp: {
     CONTACT_CODE_REGEXP: /^(0x)?[0-9a-f]{130}$/i
   }
 };
+
+
diff --git a/src/index.ts b/src/index.ts
index 3dcf687..48a3eaf 100644
--- a/src/index.ts
+++ b/src/index.ts
@@ -1,7 +1,7 @@
 const Web3 = require("web3");
 import utils from "./utils.js";
 import mailservers from "./mailservers.js";
-const constants = require("./constants");
+import constants from "./constants.js";
 
 const { utils: { asciiToHex, hexToAscii  }  } = Web3;
 
diff --git a/src/mailservers.ts b/src/mailservers.ts
index 3a74b0c..4833a64 100644
--- a/src/mailservers.ts
+++ b/src/mailservers.ts
@@ -1,4 +1,7 @@
 import mailserverList from "./data/mailservers.json";
+import constants from "./constants.js";
+
+const Topics = constants.topics;
 
 class MailServers {
   private web3: any;
@@ -60,7 +63,7 @@ class MailServers {
     });
   }
 
-  public async requestMessages(topic: string, options: any, cb?: any) {
+  public async requestMessages(topic: string|Topics, options: any, cb?: any) {
     if (this.mailserver === "") {
       if (!cb) {
         return;
@@ -68,7 +71,7 @@ class MailServers {
       return cb("Mailserver is not set", false);
     }
 
-    const topics =   [this.web3.utils.sha3(topic).slice(0, 10)];
+    const topics = [(topic in Topics) ? Topics[topic] : this.web3.utils.sha3(topic).slice(0, 10)];
     const mailserverPeer = this.mailserver;
 
     const timeout = options.timeout || 30; // seconds
diff --git a/test-mailserver.js b/test-mailserver.js
index bd55ded..e8259a3 100644
--- a/test-mailserver.js
+++ b/test-mailserver.js
@@ -1,4 +1,4 @@
-var StatusJS = require('./src/index.js');
+var StatusJS = require('./dist/index.js');
 
 (async () => {
 var status = new StatusJS();
@@ -19,4 +19,4 @@ var status = new StatusJS();
   });
 
   setInterval(() => { }, 3000);
-})()
+})();