Why are my emails going to spam? The 7 real reasons

In order of how often each one is actually the culprit.

1. Your domain isn't authenticated (SPF, DKIM, DMARC)

This is the cause more than half the time, and it's the easiest to fix. Since February 2024, Gmail and Yahoo require authentication from bulk senders — mail that fails is filtered or rejected outright. You need three DNS records: SPF (which servers may send for your domain), DKIM (a cryptographic signature proving the message wasn't altered), and DMARC (what receivers should do when the first two fail). Missing any of the three costs you inbox placement. Run a free check on your domain — it takes ten seconds and shows exactly which records are missing or broken.

2. You're mailing people who never asked

Spam complaints are the strongest negative signal a mailbox provider sees. Gmail's published threshold is a 0.3% complaint rate — above that, you're filtered regardless of authentication. Purchased lists, scraped addresses, and "we met at a conference three years ago" lists all generate complaints. Nothing downstream fixes a consent problem.

3. Your list is full of dead addresses

High bounce rates tell providers you don't know your recipients. Old lists accumulate abandoned mailboxes and spam traps — addresses that exist only to catch senders with bad hygiene. Remove hard bounces immediately and drop anyone who hasn't opened in 6–12 months.

4. Your sending domain or IP has a poor reputation

Reputation follows your domain and IP. A burst of sends from a brand-new domain looks like a spammer spinning up infrastructure — which is why new domains need gradual volume ramp-up. Check where you stand with Google Postmaster Tools, and check whether your IP or domain sits on a blocklist.

5. Missing one-click unsubscribe

Bulk senders must include the List-Unsubscribe header (RFC 8058 one-click). When unsubscribing is hard, people click "Report spam" instead — and that costs you far more than the lost subscriber. Our header analyzer tells you whether your messages carry it.

6. Content that pattern-matches spam

Content matters less than it used to, but extremes still hurt: all-image emails with no text, link shorteners, ALL-CAPS subject lines, and mismatched link text vs. destination. Write like a human sending one email to one person.

7. Sudden volume spikes

Going from 100 emails a day to 20,000 overnight is the signature of a compromised account. Ramp volume gradually — roughly doubling per day toward your target — especially on new domains or after a quiet period.

Diagnose it in 30 seconds

Start at the top of this list: authentication is the most common cause and the fastest to verify. InboxPreflight's free checker validates your SPF, DKIM, DMARC and MX records instantly — no signup, and your data never leaves your browser. If those pass, work down the list from consent to content.