Question – https://www.quora.com/How-exactly-does-a-domain-name-email-get-blacklisted-Whats-the-trigger-or-what-is-responsible-for-it
Check:
https://www.dnsbl.info/dnsbl-list.php
Email needs to have rDNS and FCrDNS, so that it is not blacklisted.
What is rDNS?
What is FCrDNS?
Remove from blacklist
https://www.ndchost.com/wiki/rbl/yahoo
Spam check: https://www.spamhaus.org/lookup/
Domain health check: https://mxtoolbox.com/domain/