diff --git a/imap-core/lib/imap-connection.js b/imap-core/lib/imap-connection.js
index 06fa4c5b..04b712b2 100644
--- a/imap-core/lib/imap-connection.js
+++ b/imap-core/lib/imap-connection.js
@@ -203,7 +203,7 @@ class IMAPConnection extends EventEmitter {
      * @param {String|Array} data If data is Array, send a multi-line response
      */
     send(payload, callback) {
-        if (this._socket && this._socket.writable) {
+        if (this._socket && !this._socket.destroyed && this._socket.readyState === 'open') {
             try {
                 this[!this.compression ? '_socket' : '_deflate'].write(payload + '\r\n', 'binary', (...args) => {
                     if (args[0]) {
diff --git a/imap-core/lib/imap-tools.js b/imap-core/lib/imap-tools.js
index fcf85b3e..5c16f792 100644
--- a/imap-core/lib/imap-tools.js
+++ b/imap-core/lib/imap-tools.js
@@ -744,7 +744,6 @@ module.exports.sendCapabilityResponse = connection => {
 
         capabilities.push('SPECIAL-USE');
         capabilities.push('UIDPLUS');
-        capabilities.push('UNSELECT');
         capabilities.push('ENABLE');
         capabilities.push('CONDSTORE');
         capabilities.push('UTF8=ACCEPT');
diff --git a/lib/pop3/connection.js b/lib/pop3/connection.js
index 7bb1973c..967bc7c0 100644
--- a/lib/pop3/connection.js
+++ b/lib/pop3/connection.js
@@ -70,14 +70,14 @@ class POP3Connection extends EventEmitter {
     }
 
     write(payload) {
-        if (!this._socket || !this._socket.writable) {
+        if (!this._socket || this._socket.destroyed || this._socket.readyState !== 'open') {
             return;
         }
         this._socket.write(payload);
     }
 
     send(payload) {
-        if (!this._socket || !this._socket.writable) {
+        if (!this._socket || this._socket.destroyed || this._socket.readyState !== 'open') {
             return;
         }
 
diff --git a/lib/tools.js b/lib/tools.js
index 914ccf82..5af63f47 100644
--- a/lib/tools.js
+++ b/lib/tools.js
@@ -459,14 +459,9 @@ function validationErrors(validationResult) {
 }
 
 function checkSocket(socket) {
-    if (!socket || !socket._writableState || !socket._readableState) {
+    if (!socket || socket.destroyed || socket.readyState !== 'open') {
         throw new Error('Socket not open');
     }
-    for (let s of [socket._writableState, socket._readableState]) {
-        if (s.destroyed || s.errored || s.closed) {
-            throw new Error('Socket not open');
-        }
-    }
 }
 
 module.exports = {