Originally Posted by noboss What should I do if I don't want my domain anymore? Is it OK to simply let the domain expired and not renew it, or should I officially notify the registrar that I will release the domain?

The best way to release a domain name is to inform your domain registrar that you don't need the domain name anymore. If you cancel the domain name, you won't get any notification emails for its renewal. If you don't cancel it and wait for the domain to get expired, your inbox will be flooded by notification emails.