Surely if you purchase a domain (domain1.com) and redirect it to your existing domain (domain2.com) you expect to loose all ranking for domain1.com. If 301's are used then the objective is simply to pass on authority, not dominate the search results with 2 domains. If you want to keep domain2.com in the index then you would take Rebecca's option 2 or 3.
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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