Link lists

I received the following email from two different vendors with the exact same text containing the exact same lists:

Hope you are well!

I updated my database with sites with 1000 + new sites which you can find in the attached files.

I have categorized my sites in 3 different files based on the prices and qualities.

Also, I have specified the blogs in tabs so that it will be easier to find blogs of a specific niche.

Kindly check and let me know about your new requirements.

Thanks!

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I know these two different people but they are obviously getting their list from the same place. I would like to find where they get this list and avoid the middle men. Any ideas on how to find the source?