Storing email address with SHA512 email address, would a substring of the sha512 value be safer to store with the email address?

Question

I am marketing to interested users with their provided email address. To make their hyperlink unique to their "offer", I plan to use SHA512 of their email address in their link address. Since the user would have the email address and now the SHA512 value, it was suggested to substring the SHA512 value instead of using the whole SHA512 value. Is that safer since the user would not have the original value and the complete hashed value?

We're aware that there are numerous solutions to make the SHA512 hash more secure, but if the substring method would work, that's what we want to implement.