GrowthStack Advisory / Cold Email Deliverability
Guide
The cold email deliverability checklist
Great messaging that never reaches the inbox performs exactly as badly as terrible messaging. Deliverability is infrastructure, and it is fixable.
Founder, GrowthStack Advisory. 10+ years building SDR and GTM systems at Locus, GoComet, and Landmark Group.
· 3 min read
The short answer
Cold email lands in spam because of infrastructure, not copy. Send from a separate domain, configure SPF, DKIM and DMARC, warm each mailbox for several weeks, keep volume per mailbox conservative, verify every address, and send plain text with almost no links in the first touch. Then monitor bounce rate and placement weekly and rotate any mailbox that degrades.
- Never send cold outbound from your primary domain
- SPF, DKIM, DMARC and a custom tracking domain are non negotiable
- Scale by adding mailboxes, never by raising volume on one
- Engagement is now a filter signal, so targeting and messaging are deliverability work
Separate your sending domain
Never run cold outbound from your primary domain. Buy lookalike domains, set them up properly, and keep your main domain reserved for existing customers and inbound conversation. One bad campaign should never threaten your company email.
Authenticate everything
- SPF authorises which servers may send for your domain
- DKIM signs your mail so receivers can verify it was not altered
- DMARC tells receivers what to do when the first two fail
- Custom tracking domain so link tracking does not inherit a shared reputation
Missing any of these makes the rest of your effort close to irrelevant.
Warm up, then stay inside sane volumes
New mailboxes need several weeks of gradually increasing, engaged sending before they carry campaign volume. After warmup, keep each mailbox conservative and add mailboxes to scale rather than pushing any single one harder. Volume per mailbox is the most common self inflicted deliverability wound.
Clean the list before you send
Bounce rate is a reputation signal. Verify every address, remove catch all domains you cannot confirm, and suppress anyone who already asked you to stop. A list that has not been verified in three months is not a list, it is a risk.
Write mail that behaves like mail
Plain text, no images, minimal links in the first message, and no attachments. Short and specific to the recipient. Spam filters increasingly measure engagement, so the strongest long term deliverability strategy is writing email people actually reply to, which is a targeting and messaging problem. See ICP, persona and messaging and AI toolstack setup.
Monitor and correct weekly
Track bounce rate, spam complaints, reply rate, and placement per mailbox. Pull any mailbox that degrades, let it recover, and rotate. Deliverability is a maintenance routine, not a one time setup.
Use the tool
Interactive tool
Outbound readiness scorecard
Twelve yes or no questions across the four things that decide whether outbound works. Answer honestly, the grade is only useful if you do.
Related reading
Questions
Why do my cold emails go to spam?+
Usually infrastructure rather than copy: missing SPF, DKIM or DMARC, insufficient warmup, too much volume per mailbox, unverified lists, or heavy links and images in the first touch.
How many emails per day can one mailbox send?+
Keep it conservative and scale by adding mailboxes rather than raising volume on any single one. Sudden volume increases on a young mailbox are a common cause of sudden spam placement.
Tell us where the funnel leaks
We will tell you honestly whether it is a targeting, execution, or qualification problem, and what it would take to fix.
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