Emails that haven't been logged into for years.

Most publicly available .txt lists are "harvested" data. They are filled with:

Laws like (Europe), CAN-SPAM (USA), and CASL (Canada) require explicit consent from the recipient. Sending to a list found via a link is a violation of these laws, which can lead to hefty fines and your website's domain being flagged as malicious. How to Build a 1,000,000+ List the Right Way

It is better to have 100,000 engaged subscribers than 1,000,000 dead ones. Regularly prune your list by removing anyone who hasn't opened an email in 90 days. This keeps your deliverability high, ensuring your emails actually land in the inbox. Conclusion