Thank you Thomas and Moosa for your feedback. After getting a little more background, these are sites the client once had in existence and have them pointing to the main site but retain their domain throughout – so they are actually aliases.
I am now thinking they set up the DNS for the aliases to mask and pointed to the main site and have unintentionally created duplicate content and multiple backlinks.
In my opinion, it would be best to remove the masking in the DNS and have the client implement a 301 for each of the alias domains to the main site. Is there a better way of correcting this issue vs a poor way?
