Will redirecting expired domains to my website help or attract penalties?

The domain authority on expired domains comes mostly from the inbound links to their deep pages. If you have similar enough content that your domain can satisfy the users that click on those links then you might get some SEO benefit from the domain redirect. To get it, you would have to put appropriate redirects in place.

For example if you find a link to:

expireddomain.example.com/blog/the-wonders-of-blue-widgets

you could redirect it to your blue widgets page:

mysite.example.com/blue-widgets

It wouldn't work to:

• Redirect it to mysite.example.com/blog/the-wonders-of-blue-widgets and give users a 404 error
• Redirect it to your home page: mysite.example.com/ which Google would view as a "soft 404" and not give the link any credit
• Redirect it to an unrelated page such as mysite.example.com/red-filanges (which wouldn't satisfy visitors).

If the links to the expired domains are spammy or paid, redirecting the expired domains to your site would hurt your rankings. It would be likely that Google would penalize your site.

This is a great idea, when handled properly.

You need to to some research about domains first

• Verify that there is not Manual Penalty to this domain (Verify it through Google Webmaster Tool )
• Check the back-links of domain if any. It might be victim of Penguin 2 & 2.1 (You can use ahref.com for example)

Redirecting domains without above verifications could lead you to hell.