Bulk sender requirements are the authentication, volume, and complaint-rate rules Google, Yahoo, and Microsoft impose on high-volume email senders, triggered at 5,000 messages a day to Gmail addresses under Google's policy.
Since February 1, 2024, Google requires anyone sending more than 5,000 messages a day to Gmail addresses to authenticate with SPF and DKIM, publish a DMARC record, keep the spam rate reported in Postmaster Tools under 0.30 percent, and support one-click unsubscribe on marketing and subscribed messages. Yahoo's bulk-sender guidance mirrors it closely: the same authentication baseline, at least a p=none DMARC record, and a working one-click unsubscribe header.
Microsoft brought Outlook into a similar regime for high-volume senders starting in 2025, and it doesn't just route non-compliant mail to spam. It rejects it outright with a 550 5.7.15 bounce.
The rule applies directly once a sender's daily Gmail-bound volume crosses that 5,000 threshold, and most real cold-outbound programs get there faster than a team expects once a handful of mailboxes are running at real scale. But the hygiene underneath the policy, real authentication, a low spam rate, an easy way out for the recipient, is worth doing well below the threshold too. The rule mostly makes explicit what a well-run sending setup already required.
Check that all three records actually pass with a header check on a real sent message, not a glance at a DNS panel that says "configured." A record that's published but misconfigured reads the same as no record at all to a receiving server.
People assume this only covers marketing blasts, not cold outbound, since "bulk sender" sounds like a newsletter problem. Cold email actually needs the authentication more, not less. A marketing list is opted in with engagement history behind it. A brand-new cold-sending domain has none of that to lean on.
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