Hi,
Depending to your HikaShop version, the email system is different (we improved it in HikaShop 2.2.2).
Which HikaShop version do you have ?
When you override an email, the override is kept during updates, like for every "overrides" in HikaShop (for views, css, mail).
Regards,
Jerome - Obsidev.com
HikaMarket & HikaSerial developer / HikaShop core dev team.
Also helping the HikaShop support team when having some time or couldn't sleep.
By the way, do not send me private message, use the "contact us" form instead.