By default, the unsubscribe macro defined in the templates or scripts is opening up a new email form with "To" as instance email ID.
How to change it
If you are using servicenow SMTP, you have an option to update the address in the SMTP account's "From"
If you have your own SMTP, you can create/update the property "glide.email.mail_to"
- Type: string
- Default value: SMTP email address that is active by default