email program fails on send with 'Exception EldProtocolReplyError

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Delphi

The following is a very basic email program program I wrote using Delph 7.
The program bombs out when executing

SMTP.Send(Email);

The message is Exception EldProtocolReplyError in Module SendEmail.exe at 00025AB4.
5.7.0 Must issue a STARTTLS command first. co1sm11098818vdc.10

program SendEmail;

{$APPTYPE CONSOLE}

uses
  SysUtils,IdSMTP,IdMessage;

 Var
  SMTP        : TIdSMTP;
  Email: TIdMessage;

begin
SMTP := TIdSMTP.Create(nil);
Email := TIdMessage.Create(nil);
try
SMTP.Host  := 'smtp.gmail.com';
SMTP.Port := 25;
SMTP.Username := 'username';
SMTP.Password := 'password';
Email.From.Address := 'steven@gmail.com';
Email.Recipients.EMailAddresses := 'steven@gmail.com';
Email.Subject := 'system message';
Email.Body.Text := 'Hello, It is Just for test';
SMTP.Connect;

// This is where the Exception occurs
SMTP.Send(Email);

finally
SMTP.Free;
Email.Free;
end;

readln;
end.

Please advice me what I need to do to make this program run.

Thank you