The FTPS MLSD/LIST commands return status code 450

Document ID : KB000113329
Last Modified Date : 07/09/2018
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Does the gateway support TLS resumption?
No, the gateway does not support TLS resumption

If the "TLS session resumption on data connection" is checked, then gateway does not allow an ftp connection. You cannot reuse TLS/SSL session ID for data connections. 

Reuse TLS/SSL session id for data connections.