Most “cold email doesn’t work” stories are really deliverability stories: the email never reached a human. Rewriting a subject line won’t help if Gmail is rejecting your domain. That’s why the order of these checks matters.
1. Are SPF, DKIM, DMARC and MX all passing?
Since February 2024, Gmail and Yahoo require bulk senders to authenticate with SPF, DKIM and DMARC,12 and Outlook followed in May 2025.3 From November 2025, Gmail moved to temporary and permanent rejections of non-compliant mail.4
How to check: send a test to a Gmail address, open the message, choose Show original, and confirm SPF, DKIM and DMARC all read PASS. If not, pause sending and fix the records. Our DNS setup guide lists every record.
2. Is the domain or IP on a blocklist?
Run each sending domain through a free multi-list checker (Spamhaus and the major lists). If it’s listed, request delisting and audit where the list came from. For a secondary cold domain, retiring it is often cheaper than nursing it back.
3. Is your bounce rate over 2%?
High bounces almost always mean unverified or old data. Stop the campaign, re-verify the whole list, and remove invalid, role (info@) and disposable addresses. Healthy is under 1%.
4. Is the domain at least 30 days old and warmed?
New domains are watched more closely. The default is a domain at least 30 days old, with mailboxes warmed for 3–4 weeks before the first cold email, then 10 cold emails a day rising slowly to 15–25. Only time fixes this one.
5. Is it one provider, or everywhere?
Split your reply rate by the recipient’s email provider: Google, Microsoft or other. Look up each prospect company’s MX record, label it, and compare. If one provider is far below the others, cut volume to it and send Google-run companies from Google mailboxes and Microsoft-run ones from Microsoft mailboxes.
6. Does a placement test flag your copy?
Run a seed test with your real email, not a sample. If it’s flagged, remove links and images from the first email, cut salesy words, and send plain text. A Promotions-tab result on a personal seed inbox is a content warning, not a verdict, because most B2B buyers sit behind business filters.
7. If everything passes, is it reputation?
If everything above passes, the cause is usually too much volume, too many complaints, or the wrong people. Halve volume, rotate in warmed spare mailboxes, tighten targeting, and give it 4–8 weeks. Keep spam complaints under 0.1%, and never let them reach 0.3%, Gmail’s ceiling.1
Which signals should you trust?
| Signal | Trust it? |
|---|---|
| Reply rate by recipient provider | Best signal |
| Reply rate by mailbox | Yes |
| Bounce rate | Yes |
| Seed placement test | Useful, but noisy for B2B |
| Google Postmaster Tools spam rate | Only if you send enough to personal Gmail to see data5 |
| Warm-up “health score” | Measures warm-up only |
| Open rate | No. Turn tracking off. |
Common questions
Why are my cold emails going to spam?
The most common causes, in order: SPF, DKIM or DMARC not passing; a blocklisted domain; bounces over 2% from an unverified list; a domain under 30 days old or not warmed up; one provider filtering you; spammy copy with links or images; and a damaged reputation from too much volume or too many complaints.
How do I know if my cold emails are landing in spam?
Watch reply rate split by mailbox and by the recipient’s email provider. A mailbox or provider that suddenly goes quiet while others hold steady is usually landing in spam. Seed placement tests help, but treat them as a smoke alarm rather than proof.
How long does it take to fix a domain’s reputation?
If the cause was volume, complaints or targeting, halve your volume, rotate in warmed spare mailboxes, tighten targeting and give it 4 to 8 weeks. A blocklisted cold domain is often cheaper to retire.
Keep reading
Sources
- Google: Email sender guidelines. support.google.com
- Yahoo: Sender best practices. senders.yahooinc.com
- Microsoft: Outlook requirements for high-volume senders, 2025. techcommunity.microsoft.com
- Spam Resource: Gmail enforcement ramps up, November 2025. spamresource.com
- Suped: Postmaster Tools reputation dashboards discontinued. suped.com