Hi,
Okay ; so you can activate the option "send_mail_subsale_update_main" in your HikaMarket configuration.
In HikaMarket 1.6.5 ; that option is hidden but it will be available in the next release (but I still need a good label for that setting).
For the moment, the best is to add that setting directly in your database.
INSERT INTO #__hikamarket_config (config_namekey, config_value, config_default) VALUES ('send_mail_subsale_update_main', 1, 0);
(where you have to replace "#_" with your database prefix.. Like "jos_hikamarket_config")
Regards,