Everyone blames spam words. “Free,” “guarantee,” “act now” — swap them out and you’ll be fine, the advice goes. It’s mostly a myth. Modern spam filters weigh reputation and authentication far more heavily than vocabulary. You can write the cleanest email in the world and still hit the junk folder if the plumbing underneath is wrong.
Here’s what actually decides whether you reach the inbox, roughly in order of impact.
1. Authentication: SPF, DKIM, DMARC
These three DNS records prove you’re allowed to send from your domain. As of 2024, Google and Yahoo require them for bulk senders, and it’s only gotten stricter since. If they’re missing or misconfigured, you’re filtered before a filter even reads your words.
- SPF lists which servers may send for your domain.
- DKIM cryptographically signs your mail so it can’t be forged.
- DMARC tells receivers what to do if the first two fail — and gives you reporting.
This is a one-time setup that fixes more deliverability problems than any subject-line tweak ever will.
2. Sender reputation and warm-up
Mailbox providers score your domain and IP on history. A brand-new domain sending 500 emails on day one looks exactly like a spammer. Warm up gradually — start with a handful of emails a day and ramp over two to four weeks — and keep daily volume per inbox modest (many teams cap around 30–50 cold sends per inbox per day and add inboxes to scale).
3. List quality and bounce rate
Every hard bounce is a black mark. Send to a stale, unverified list and your bounce rate spikes, reputation drops, and even your good emails start landing in spam. Keep bounces under 2% by verifying before you send — this is the single most controllable factor after authentication.
4. Engagement signals
Opens, replies, and “not spam” clicks tell providers people want your mail. Low engagement and spam-complaints do the opposite. Which is why targeting matters: a tightly-matched list to people who might actually care beats a huge generic blast, every time.
5. Then — and only then — content
With the fundamentals right, content hygiene is the finishing touch, not the foundation:
- Keep it short and personal; avoid heavy HTML, big images, and link-stuffing.
- Include a real, plain-text unsubscribe path.
- Don’t use link shorteners — they’re heavily associated with spam.
- Ease off the most obvious trigger phrases, but don’t obsess; they’re a minor factor.
A quick pre-send checklist
- SPF, DKIM, and DMARC all pass ✔
- Domain warmed up, volume paced ✔
- List verified, bounce risk removed ✔
- Targeting tight enough to earn replies ✔
- Copy short, human, one clear ask ✔
Scan your copy in seconds
Our free Spam-Word Checker flags the phrases worth softening — the last 10% once your fundamentals are solid.
Written by the Verisignal team. Verisignal delivers pre-verified leads so your bounce rate stays low and your sender reputation stays intact. Get a verified list →