The second option requires a bit more time and effort than a 301 redirect. You could do a mini overhaul of the site and turn it into a microsite for your main domain. This option is good for exact-match domains for your targeted keyword, and there are other reasons for going the microsite route that Rand's highlighted in his post about root domains, subdomains, subfolders and microsites. This strategy also works better if the old domain has decent rankings for the keywords you're targeting.
If it contains any of those, then I am going to crawl it. Otherwise, I'm not going to because it's probably just something like an Amazon listing. Okay lets move on to the endless cruel. So this is the endless crawl. Basically, here you put your seed websites, one will do if it's a big website, because there's probably loads of domains on it. If it's a tiny, tiny a website, then you might want to stick a few more in so, as I was saying before, it will crawl on all the pages on these websites and then for each external domain that it finds on that website. It will check whether it's expired if it's not expired, it'll try and crawl it and then it will start the loop again, it'll try and take all the domains from there check that they are expired.
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