Hi,
Our emails has been test on spam tests, I don't think the problem is linked with the content of the email but with the configuration of your email server (reverse name, hostname, dkim, etc).
So, please use a spam mail tester like :
www.mail-tester.com/
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.