update

ts/mail/delivery/smtpserver/data-handler.ts

@@ -1139,6 +1139,18 @@ SmtpLogger.debug(`Parsed email subject: ${subject}`, { subject });
    * @param response - Response message
    */
   private sendResponse(socket: plugins.net.Socket | plugins.tls.TLSSocket, response: string): void {
+    // Check if socket is still writable before attempting to write
+    if (socket.destroyed || socket.readyState !== 'open' || !socket.writable) {
+      SmtpLogger.debug(`Skipping response to closed/destroyed socket: ${response}`, {
+        remoteAddress: socket.remoteAddress,
+        remotePort: socket.remotePort,
+        destroyed: socket.destroyed,
+        readyState: socket.readyState,
+        writable: socket.writable
+      });
+      return;
+    }
+    
     try {
       socket.write(`${response}${SMTP_DEFAULTS.CRLF}`);
       SmtpLogger.logResponse(response, socket);