How to setup a medium content website redirect for a migration in 30 minutes

Hello there!

During the Rayvan re-branding to RayvanBros at the beginning of the year - we decided to leave our heavily seo-friendly website rayvan.net to become secondary - in order to migrate the individual page strength, we redirected relevant content to their newly due places. Leaving every other page to become a custom Page Not Found web page (404 error code) that leads back to the new website.

On the same topic - We were recently consulted for a private government contract to advise a realistic recommendation for migrating a 15,000+ page website into Drupal. But please do understand this is a totally different animal - although we are not talking about animals. Pages with 500+ pages should be systematically migrated.