When a plain FTP connection is attempted to SecureTransport, the client is met with an error message as the below one and the connection fails.

530 SSL is mandatory

Resolution

The "530 SSL is mandatory" reply means that the SecureTransport Server accepts only SSL/TLS encrypted FTP (FTPS) connections for the specific user, or for the whole server in general. The recommended solution is to advise the clients to use FTPS, as it is more secure than the plain FTP.

However, if plain FTP is desired, then the encryption requirement can be removed as shown below:

1. Login to the Admin UI

2. Go to the Access > Secure Sockets Layer page

3. Under the SSL Encryption Entries section, edit the configuration for the user class which the said user belongs to (if such a class was configured) or the configuration for all users (the class *)

4. Change the Encryption setting to Optional and save it

5. Restart the FTP service

Additional Note

If the users connect to the ST environment over an ST Edge server, the above changes will have to be done on the Edge as well.