IMAP "Force Usage of SSL/TLS" Setting

1

On Wikipedia it says:

“An IMAP server typically listens on port number 143. IMAP over SSL/TLS (IMAPS) is assigned the port number 993.”

As per the Microsoft documentation, Port 993 is obviously the correct port.

However, why is Port 993 considered legacy in eM Client and Port 143 the recommended port to force usage SSL/TLS?

Screenshot:

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2

Legacy just means the connection can go straight to SSL without any negotiation.

It is more efficient that way.