Gmail and Yahoo bulk sender checker
Paste the headers of an email you sent, and see whether it meets Gmail's and Yahoo's sender requirements: SPF, DKIM, DMARC, alignment, one-click unsubscribe, TLS and reverse DNS.
Runs in your browser. Nothing is uploaded.
What it checks
The checker reads the Authentication-Results header your mailbox provider added, so it reports what Gmail or Yahoo actually concluded, not what your DNS says should happen. It checks that SPF and DKIM passed, that DMARC passed, and that the From domain aligns with at least one of them. For marketing mail, it checks for one-click unsubscribe (both List-Unsubscribe headers, an https link, and a DKIM signature that covers them). From the Received headers, it checks TLS and the sending server's reverse DNS.
To check a domain's DNS records without sending anything, use the email health checker. For what each requirement means and how to meet it, read the Gmail and Yahoo requirements guide.
Frequently asked questions
How do I get an email's headers?
In Gmail, open the message, click the three-dot menu (⋮) and choose Show original, then Copy to clipboard. In Outlook on the web, open the message, choose ⋯ → View → View message source. In Yahoo Mail, choose ⋯ → View raw message. Send a real message from your app or newsletter tool to your own inbox first, and check that one.
What are Gmail's and Yahoo's bulk sender requirements?
Since February 2024, senders of about 5,000 or more emails a day to Gmail must authenticate with SPF and DKIM, publish DMARC (p=none is enough), align the From domain with SPF or DKIM, offer one-click unsubscribe on marketing mail, keep spam complaints under 0.3%, use TLS and have valid reverse DNS. Yahoo's rules are nearly the same. Our requirements guide explains each one.
Does this tool send my email headers anywhere?
No. The check runs entirely in your browser. Nothing you paste is uploaded or stored. Headers contain addresses and server names, so this matters.
Why can't the checker show my spam complaint rate?
Because it isn't in the message. Gmail reports your complaint rate per domain in Google Postmaster Tools, which you set up once by verifying your domain. Keep it under 0.3%, and ideally under 0.1%.
My transactional emails fail the unsubscribe check. Is that a problem?
No. One-click unsubscribe is required for marketing and promotional mail, not for receipts, password resets or account alerts. The checker flags a missing header as something to check, not a failure.
Something failing?
Our deliverability fix sorts out SPF, DKIM, DMARC and reverse DNS for $199, on whatever provider you use.