you can get duplicate panelty from Google if you have the same exact content on two websites.
If you see someone's rankings have slipped then it's possible that site's page contents have been duplicated causing a duplicate content penalty.
Google doesn't want multiple copies of the same content cluttering their results pages so it will devalue all but one of the copies of the content based on the age of the page.
You can't say for sure how much duplication can result in a penalty, if it's 10 words, 20, a paragraph or a whole page...
YES! you can use 301 redirect to redirect to your mail website. This will save you from the panelty.
seo_expert
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