What are the bulk sender requirements?
Since February 2024 Gmail and Yahoo, and since May 2025 Microsoft Outlook.com, require anyone sending around 5,000 or more messages a day to their users to authenticate mail with SPF, DKIM and DMARC, keep spam complaints low, and offer one-click unsubscribe. Mail that fails is throttled, sent to spam or rejected.
The requirements side by side
| Requirement | Gmail | Yahoo | Outlook.com | Checked here |
|---|---|---|---|---|
| SPF record | Required | Required | Required | Yes |
| DKIM signature | Required | Required | Required | Yes (by selector) |
DMARC, at least p=none | Required | Required | Required | Yes |
| From domain aligned with SPF or DKIM | Required | Required | Required | Check a sent message |
| Forward and reverse DNS on sending IPs | Required | Required | Recommended | Check with reverse DNS lookup |
| TLS for sending | Required | Required | — | Check yourself |
| One-click unsubscribe (RFC 8058) | Required for marketing | Required for marketing | Recommended | Check your mail headers |
| Spam rate under 0.3% | Required | Required | — | Google Postmaster Tools |
The tool proves what DNS can prove — SPF, DKIM and DMARC — and lists the rest as "check yourself", with how. It never marks something as passing that it cannot see.
How to meet each requirement
SPF. Publish one TXT record at the domain listing every service that sends as you, ending in ~all or -all. Build it with the SPF generator and verify the lookup count with the SPF checker.
example.com. TXT "v=spf1 include:_spf.google.com include:sendgrid.net ~all"DKIM. Turn on DKIM signing at each sending service and publish the key it gives you at selector._domainkey. Use 2048-bit keys. Confirm with the DKIM checker.
DMARC. Publish a policy at _dmarc. p=none meets the rule; once reports show your own mail passes, move to quarantine or reject. The DMARC generator builds the record.
_dmarc.example.com. TXT "v=DMARC1; p=none; rua=mailto:dmarc-reports@example.com"Alignment. The domain in the visible From: address must match the SPF domain (Return-Path) or the DKIM d= domain. Newsletters sent through a platform with its own Return-Path pass via DKIM — so set up DKIM with your own domain at the platform.
Checking the parts DNS cannot show
- Alignment and DKIM in practice: send a message to a Gmail address, open it, choose *Show original*, and check that SPF, DKIM and DMARC all say PASS.
- Reverse DNS: look up each sending server's IP with the reverse DNS lookup. It needs a PTR name that resolves back to the same IP. Hosted providers handle this for you.
- One-click unsubscribe: marketing mail needs both headers below, and unsubscribes must be processed within two days.
- Spam rate: register your domain in Google Postmaster Tools and keep the user-reported spam rate below 0.3%, ideally below 0.1%.
List-Unsubscribe: <https://example.com/unsub?id=123>, <mailto:unsub@example.com>
List-Unsubscribe-Post: List-Unsubscribe=One-ClickWho the rules apply to
The strict rules apply to bulk senders: Gmail defines that as close to 5,000 or more messages a day to personal Gmail accounts, Microsoft as more than 5,000 a day to Outlook.com, Hotmail and Live addresses. Once you cross the line on any day, Gmail treats you as a bulk sender permanently. Every sender, however small, still needs SPF or DKIM, valid reverse DNS and a low spam rate.
What happens if you do not comply
Gmail began rejecting a share of non-compliant bulk mail in 2024 and, from November 2025, stepped up to temporary and permanent rejections, with SMTP errors that name the missing requirement (for example 5.7.26 for unauthenticated mail). Outlook.com sends non-compliant mail to junk and then rejects it with 550 5.7.515. Yahoo defers or rejects. Fixing DNS records takes effect as soon as they propagate, usually within an hour.