Email Addresses, Public Domain and US, India and EU Data Protection

You are right in thinking that a publicly listed email on the website is free to hand out, but the GDPR requires also to use personal data (i.e. email address) for the purposes for which are given. If someone lists the email address on his/her website, he/she wants to be contacted about his/her own activity (i.e. as a book blogger) they are not giving their consent to be inserted in an email database. 

You should contact them and ask for consent, even with automatic means, by asking them to be inserted in an email database for that purpose. You can imagine it as a service (something like “do you want to be updated with new authors publication?” or whatever your marketing team could imagine) and you need to ask them to consent to the transfer their address to third parties (authors).

Here you can find some articles about privacy policy and consent:

• Everything you need to know about the GDPR Privacy Notice: https://advisera.com/articles/gdpr-privacy-notice-6-key-elements-to-include/
• Is consent needed? Six legal bases to process data according to GDPR: https://advisera.com/eugdpracademy/knowledgebase/is-consent-needed-six-legal-bases-to-process-data-according-to-gdpr/ 
• Four main questions for obtaining and managing data subjects’ consent under GDPR: https://advisera.com/eugdpracademy/knowledgebase/four-main-questions-for-obtaining-and-managing-data-subjects-consent-under-gdpr/
• Email marketing in the era of GDPR – How to ensure compliance? https://advisera.com/eugdpracademy/blog/2019/05/27/gdpr-and-email-marketing-rules-for-compliant-campaigns/

These materials will provide further help:

• EU GDPR document template Privacy Notice: https://advisera.com/eugdpracademy/documentation/privacy-notice/

• EU GDPR Foundations Course: https://advisera.com/training/eu-gdpr-foundations-course//