Hello,
It depends how your vendor creates its account.
The "vendor_admin_registration" email is generated by the "register" function of the Vendor.
It uses by default the "from email" HikaShop setting but yes, the email can be configured directly in the HikaShop email edition page.
Since it uses the HikaShop email system, all sent emails can be saved in the HikaShop email history system.
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.