Gmail, Yahoo and Microsoft sender requirements checker
Check a domain against the bulk sender requirements of Gmail, Yahoo and Outlook.com, rule by rule, and get a badge for your site.
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How the sender requirements check works
Gmail, Yahoo and Microsoft each publish rules for anyone who sends them mail, and stricter ones for bulk senders. This checker reads a domain’s public DNS once and shows, for each provider, which rules are met, which aren’t, and which only a real message can show.
What is checked
tanase.ai’s server looks up the domain’s SPF, DMARC, MX, MTA-STS, TLS-RPT and BIMI records, and the same 60 DKIM selectors the DKIM checker tries once it knows the domain exists. It follows every SPF include to count the 10 lookups SPF allows, walks up to the parent domains when the domain has no DMARC record of its own, and resolves the first five mail servers with their reverse DNS. When the SPF record lists single sending addresses (ip4: or ip6: without a range), the first three get a forward-confirmed reverse DNS check, as Gmail and Yahoo require for sending IPs.
The whole check stops after 12 seconds. A lookup still unanswered then, or one that failed, is shown as “couldn’t check”, never as missing, and the result isn’t cached. A finished result is cached for two minutes; Check again runs it afresh.
How each provider is judged
Each provider’s rules are listed as that provider writes them, with a link to its page and the date we last read it. Rules that DNS can show are judged: SPF must be one valid record within 10 lookups; DKIM needs an RSA key of 1024 bits or more at one of the selectors (an Ed25519 key on its own is a warning, because Gmail needs RSA); DMARC needs a valid record with p=none or stricter. A provider meets its rules when every one of these passes, partly meets them when something needs a look, such as no DKIM key at the common selectors, which isn’t proof DKIM is off, and doesn’t meet them when one fails.
Alignment is shown as readiness: a DKIM key under your domain means mail signed with your domain can align, while SPF alone aligns only when the Return-Path uses your domain, which DNS can’t show. Spam rate, TLS, unsubscribe headers and message format never change the verdict: they are marked for a test message or for the provider’s own dashboards. Optional records (MTA-STS, TLS-RPT and BIMI) are listed apart and don’t count either.
The badge
The embeddable badge shows Gmail, Yahoo and Microsoft with the same verdicts as this page, the domain and the date of the check. It is served from its own address with its own rate limit, cached at the edge for 12 hours and in browsers for one hour, so it never claims a result older than about 13 hours. To see the reasons behind a badge, open its link: it runs this page’s check for that domain. For the whole setup graded out of 100, use the deliverability score; for a real message, the email test; for one record, the SPF checker or DMARC checker.
Updated · Maintained by Liviu Tanase
Questions
What are the Gmail sender requirements?
Since February 2024 everyone who sends to personal Gmail accounts needs SPF or DKIM, valid forward and reverse DNS for the sending IPs, TLS, a spam rate below 0.3% in Postmaster Tools and messages formatted to RFC 5322. Bulk senders, more than 5,000 messages a day to Gmail, also need both SPF and DKIM (an RSA key of 1024 bits or more, 2048 recommended), a DMARC record (p=none is enough), a From: domain aligned with the SPF or DKIM domain, and one-click unsubscribe in marketing mail. This checker tests the DNS part; the SPF checker, DKIM checker and DMARC checker show each record in detail. The rules are on Google’s sender guidelines page.
What are the Yahoo sender requirements?
Yahoo asks all senders for SPF or DKIM, a spam rate below 0.3%, valid forward and reverse DNS for the sending IPs and compliance with RFC 5321 and 5322. Bulk senders (Yahoo sets no number) also need SPF and DKIM, a DMARC policy of at least p=none that passes, a From: domain aligned with SPF or DKIM (relaxed alignment is fine), and one-click unsubscribe honoured within 2 days. Yahoo strongly recommends a rua report address and recommends DKIM keys of 1024 bits or more. Source: Yahoo’s sender best practices.
What does Microsoft require from high-volume senders to Outlook.com?
Domains sending more than 5,000 emails a day to Outlook.com, Hotmail and Live addresses must pass SPF and DKIM and publish DMARC with at least p=none, aligned with SPF or DKIM (preferably both). Since 5 May 2025 Outlook.com rejects mail that fails with 550 5.7.515. Microsoft also recommends a From or Reply-To address that can receive replies (this checker looks for working MX records), working unsubscribe links and list hygiene. Source: Microsoft’s announcement.
What can’t a DNS check show?
Anything that depends on the mail itself: whether a real message is aligned (its Return-Path and DKIM d= against its From:), whether it arrived over TLS, whether it carries the one-click List-Unsubscribe headers, and whether its Message-ID and Date are valid. Those rows say Check with a test message: send one to the email test and it replies with all of them. Spam rate is visible only to the providers, in Google Postmaster Tools and Yahoo’s feedback loop.
How does the badge work?
Copy the HTML or Markdown snippet under your result. The badge is an image that runs the same check on its own, is cached for up to 12 hours at the edge and an hour in browsers, shows the date it was checked and links back to this page. When a lookup fails or times out it says “couldn’t check” instead of a verdict, and that answer isn’t cached. It is a static SVG with no scripts, and any site can show it.
How is this different from the deliverability score?
The deliverability score grades a domain’s whole mail setup out of 100. This checker asks a narrower question, whether the domain meets what Gmail, Yahoo and Microsoft require, and answers per provider and per rule. Both use the same lookups and the same SPF, DKIM and DMARC rules, so they agree.