In short
- Check SPF, DKIM, and DMARC first — most spam problems start here.
- Then list quality: invalid addresses cause bounces, which cost reputation.
- Then pattern: sudden volume spikes look like abuse.
- Content and reputation come last, not first.
Step 1 — Authentication
If SPF, DKIM, and DMARC are missing or misaligned, major providers treat your mail as unverified. This is the single most common cause and the easiest to fix, because it is entirely under your control in DNS.
- Look up your domain's SPF record and confirm it authorises your actual sending server.
- Confirm a DKIM public key exists for the selector your SMTP signs with.
- Confirm a DMARC record exists and that SPF or DKIM aligns with the From domain.
Step 2 — List quality
Hard bounces from addresses that do not exist are read as a sign you did not collect the list properly. Purchased and scraped lists also contain spam traps, which cause immediate and lasting damage.
- Remove syntax-invalid addresses before sending.
- Deduplicate, including case and whitespace variants.
- Remove addresses that hard-bounced previously.
- Never send to a purchased list.
Step 3 — Sending pattern
A new domain that suddenly sends 100,000 messages looks exactly like an abused domain. Warm up over days or weeks: start small, keep volume steady, and only increase while bounces and complaints stay low.
Step 4 — Content
- Include a plain-text alternative alongside the HTML.
- Keep the image-to-text balance reasonable.
- Avoid link shorteners and mismatched link text.
- Include a visible unsubscribe link and unsubscribe headers.
- Avoid ALL CAPS subjects, excessive punctuation, and urgency stacking.
Step 5 — Reputation
If authentication, list, pattern, and content are all clean and mail still goes to spam, the domain or sending IP reputation is likely already damaged. Recovery is slow: reduce volume, send only to engaged recipients, and rebuild over weeks. Consider a separate subdomain for marketing mail.
Checklist
- SPF published and authorising the real sender.
- DKIM key published for the signing selector.
- DMARC published with alignment passing.
- List cleaned, deduplicated, bounces removed.
- Volume ramped gradually, not spiked.
- Plain-text alternative and unsubscribe present.
Run these checks now
Questions people ask
How long does it take to recover from spam placement?
Fixing DNS records can change results within a day or two. Rebuilding a damaged domain reputation takes weeks of low-volume, high-engagement sending.
Can any tool guarantee the inbox?
No. Tools identify and reduce known risks. The receiving provider makes the final placement decision.
Should I send marketing mail from a subdomain?
Often yes. It keeps campaign reputation separate from your transactional and person-to-person mail.