For most of email's history, weak authentication was a silent problem: your mail still arrived, fraud was someone else's story. That era is ending. In February 2024, Google and Yahoo began requiring email authentication (SPF, DKIM, DMARC) from anyone sending in volume to their users — and Microsoft now applies the same requirements (Outlook, 2025). Between Gmail, Yahoo, and Microsoft 365, these providers sit in front of an enormous share of business and consumer mailboxes — and across the board they filter or reject unauthenticated mail far more aggressively than before.

What the requirements look like

The published sender requirements center on exactly the records our scan reads:

  • SPF and DKIM configured for your sending domain.
  • A DMARC record published (at minimum p=none for bulk senders — with the stated direction of travel toward enforcement).
  • Alignment between the authenticated domain and the visible From address.
  • Low spam-complaint rates and one-click unsubscribe for bulk senders.

Mail that fails these checks is increasingly filtered to spam or rejected outright — sometimes refused at the SMTP level with an error code your customers never see, sometimes quietly diverted to a spam folder no one checks.

Who this affects (hint: not just bulk senders)

The strictest published thresholds target bulk senders, but the enforcement machinery evaluates authentication on all inbound mail. Small businesses feel it as a quiet symptom: quotes that "never arrived," invoices customers swear they didn't get, follow-ups landing in spam. Deliverability failure rarely announces itself — it looks like customers ignoring you.

The double cost of weak authentication

  1. Fraud exposure: without DMARC enforcement, your exact domain can be spoofed.
  2. Delivery failure: without clean SPF/DKIM/DMARC, your own legitimate mail increasingly doesn't arrive.

The same remediation fixes both: authorize your legitimate senders, align authentication, move your policy to enforcement.

Check whether your domain passes

The records the mailbox giants check are public DNS. Run the free scan and see in 10 seconds where your domain stands against them.