Hello,
As I wrote you in another thread, you already have the vendor attributions in the HikaShop mail data.
So you can process them and change the field you want (via an override).
The modification of the "reply" is a good solution to avoid some issues with spam filters ; because sending email as your vendor might not be appreciated by antispams.
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.