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.
What do you use for MS? I know live.com still struggles with this. Though I did create a rule that junked every email with no valid SPF record, so that helps.
It was a work issue about a decade ago. Client wanted certain emails from automation to be masked as coming from him.
Most email boxes, including Gmail, didn’t have an issue. Outlook(the one that shipped with Office) laughed at it and displayed the original sender in giant bold letters.