What is the smtp 'noop' command used for?

@daisha 

The SMTP 'noop' command (short for "no operation") is used to check the connection between the client and server. It does not perform any actual operation but is commonly used as a keep-alive message to prevent the connection from timing out. When the 'noop' command is issued, the server responds with an acknowledgment, indicating that the connection is still active.