procedure TForm1.btnGetClick(Sender: TObject);
var
  MsgUids: TStrings;
begin
  if clIMAP4.Active then Exit;

  clIMAP4.Server := 'mail.test.com';
  clIMAP4.UserName := 'test';
  clIMAP4.Password := 'test';
  clIMAP4.Open();

  clIMAP4.SelectMailBox('INBOX');

  MsgUids := TStringList.Create();
  try
    clIMAP4.UidSearchMessages('SUBJECT hello', MsgUids);

    if (MsgUids.Count > 0) then
    begin
      clIMAP4.UidRetrieveMessage(MsgUids[0], clMailMessage1);

      ShowMessage('From: ' + clMailMessage1.From.FullAddress + #13#10 +
        'Subject: ' + clMailMessage1.Subject);
    end;
  finally
    MsgUids.Free();
  end;

  clIMAP4.Close();
end;