Google has started automatically blocking emails sent by bulk senders who don’t meet stricter spam thresholds and authenticate their messages as required by new guidelines to strengthen defenses against spam and phishing attacks.
As announced in October, the company now requires those who want to dispatch over 5,000 messages daily to Gmail accounts to set up SPF/DKIM and DMARC email authentication for their domains.
It blows my mind that some of the largest email services in the world were accepting mail without all the antispam authentication. Everybody had been doing their best to keep it in check and they were simply ignoring all of it?