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Why your emails go to spam — and how to prove it in 30 seconds

If your email lands in spam, it is rarely the subject line. Gmail, Outlook and Yahoo decide placement on authentication, sender reputation and engagement signals — long before they read a word. Here is what they actually check, in the order that matters.

Why mailbox providers enforce this

Since February 2024, Gmail and Yahoo enforce bulk-sender rules: authenticated SPF and DKIM, a published DMARC policy, a one-click List-Unsubscribe header, and a spam-complaint rate under 0.3%. Miss any one and your mail is filtered or rejected outright — regardless of content quality. Mailbox providers treat authentication as identity: if they can't verify who sent the message, they assume the worst.

How to fix it

  1. Authenticate the sending domain: SPF, DKIM and an aligned DMARC policy (p=quarantine or p=reject, not p=none).
  2. Add a List-Unsubscribe header with one-click (RFC 8058) support — now mandatory for bulk senders.
  3. Check the sending IP and domain against the major blocklists (Spamhaus, Barracuda).
  4. Warm the domain gradually if it's new — volume spikes from a cold domain read as spam.
  5. Keep spam complaints under 0.3% — prune unengaged recipients.
  6. Run a real test: send one email to Folderly Flash and see exactly which of these is failing for your message.
Don't guess — measure it. Send one email to Folderly Flash and see exactly which checks pass or fail for your message, in 30 seconds. No signup.
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FAQ

Does spammy wording send emails to spam?
Far less than you'd think. Modern filters weight authentication and reputation over content. A perfectly worded email from an unauthenticated domain still lands in spam; a plain email from a well-authenticated, reputable domain reaches the inbox.
Why do my emails go to spam only on Gmail?
Gmail leans heavily on domain reputation and engagement history. If Gmail users rarely open or reply, Gmail down-ranks you specifically, even when Outlook still inboxes. This is why per-provider inbox-placement testing matters.
How fast can I fix it?
Authentication and List-Unsubscribe fixes are DNS/header changes that take minutes to publish and up to 48 hours to propagate. Reputation recovery takes longer.

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