Yes, this is possible. Please navigate to Admin > Workflows > Email Notification > Template > Agent Reply Template and click on "insert placeholder which would give you the placeholders available in the system. Kindly choose the placeholder "{{ticket.portal_url}}” under helpdesk options to add it in your reply and position it according to your preference.

This will insert a product-specific ticket URL inside a ticket rather than the generic ticket URL which would map the customers to the right portal.