Why are my emails going to spam? A diagnostic, in order
"Why are my emails going to spam?" is the most-asked question in email — and most answers to it start in the wrong place, fiddling with subject lines while the real cause sits in DNS or in the list itself.
Spam placement is a scoring decision: mailbox providers weigh identity, history, audience response, and content — roughly in that order of importance. So diagnose in that order. Here's the checklist, most-likely culprit first.
1. Authentication (check this first, always)
If SPF, DKIM, or DMARC is missing or misaligned, stop — nothing else matters until this is fixed. Since the 2024 Gmail/Yahoo rules, bulk senders without proper authentication don't have a deliverability problem, they have a delivery problem: mail gets rejected or junked on identity alone.
Quick test: send to a Gmail account you own, open the message, and use "Show original." You want to see SPF: PASS, DKIM: PASS, DMARC: PASS — all three, on the domain you actually send from. If any fail, fix DNS before reading further. (Our SPF/DKIM/DMARC guide walks through it.)
While you're in DNS-land: confirm you're not sending bulk mail from your bare root domain, and that reverse DNS on your sending IPs resolves (your platform's job — but verify once).
2. List quality and consent
The second-most-common cause, and the least glamorous:
- Bounce rate over 2%? You're mailing a decayed or unverified list, and providers are reading it as scraping. Verify and cut.
- Complaint rate approaching 0.3%? People are telling Gmail your mail is unwanted, and Gmail believes them.
- Old or imported addresses in the mix? A single spam-trap address — a dead mailbox providers resurrect specifically to catch bad senders — can tank placement on its own, and traps live precisely in old lists.
If you bought a list at any point: that's your answer. There is no deliverability fix for a purchased list except deleting it.
3. Engagement history
Mailbox providers watch what recipients do: open, read, reply, delete-without-reading, ignore. A sender whose mail is chronically ignored drifts spamward even with perfect authentication and clean lists.
The usual driver is over-mailing a mostly-cold list. The counterintuitive fix: send less, to fewer people. Cut back to your engaged segment (clickers in the last 90 days), rebuild positive signals for a few weeks, then expand gradually — essentially re-running a warm-up. Sending more to "make up for" spam placement is the one move guaranteed to make it worse.
4. Content (yes, last)
Content matters far less than folklore says — see the "spam trigger words" myth we'll take apart next week — but a few things do get scored:
- Link reputation. Every domain you link to lends you its reputation. One link to a flagged domain (including some URL shorteners) can junk an otherwise clean send.
- Image-only emails with no real text — a classic filter-evasion pattern, scored as such.
- Mismatched or sloppy HTML, hidden text, and form embeds.
- A missing or buried unsubscribe link — both a legal problem and a filter signal.
5. Verify your fix
Placement isn't guessable from your send dashboard. Set up Google Postmaster Tools (free; shows your domain reputation and spam rate as Gmail sees them) and run seed tests: send to your own fresh Gmail/Outlook accounts that have never interacted with your mail and see where it lands.
Then give it time. Reputation recovers on a lag — expect a few weeks of clean sending before placement follows.
The bottom line
Spam placement is almost never a subject-line problem. Work the order — identity, list, engagement, content — and you'll find the cause in the first two steps far more often than not. Fix the foundation, send wanted mail to people who asked for it, and the inbox follows.