421 sorry cleartext sessions are not accepted on this server

Sometimes we get a error Message when using the FTP clients: 421 Sorry, cleartext sessions are not accepted on this server.

Problem: This error mean that the FTP provider has secured the access with Transport Layer Security (TLS) or its predecessor, Secure Sockets Layer (SSL).

Solution:

Change the protocol of the host to “ftpes://”

The configuration will be

Host: ftpes://hostname.com
port: 21

a) Login to WHM
b) Go To : Service Configuration 
c) Click on : FTP Server Configuration

and set

TLS Encryption Support : to “Optional