To monitor the SSL certificate of an FTPS server, Implicit mode is the recommended method. In this mode, the connection is automatically encrypted as soon as the client connects, making it ideal for monitoring SSL certificates.

• Overview: In Implicit FTPS mode, the client initiates an SSL/TLS connection immediately upon connecting to port 990. There is no need for an explicit STARTTLS or AUTH TLS command, as encryption is enabled automatically.
  

• Monitoring SSL Certificate: For monitoring the SSL certificate of an FTPS server, you should use Implicit mode on port 990.
  

• Explicit mode (typically using port 21) requires the client to explicitly request encryption by sending the appropriate FTP command (e.g., STARTTLS). Since this command is not automatically triggered by Applications Manager, an insecure connection may result, or the connection may fail altogether.

Notes

1. Use Implicit mode (port 990) for SSL certificate monitoring.
   
2. Explicit mode (port 21) does not automatically initiate encryption and may not be suitable for reliable certificate monitoring.