Hi,
Did you made some email overrides ?
A PHP error in the email could stop the mail processing.
You can test your emails by modifying an order in the backend. Just change the order status to "confirmed" and select "notify customer : yes".
At this moment, you would see the email content that HikaShop would send. It's a good trick to see email content !
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.