Email Deliverability: How to Land in the Inbox, Not Spam
Technical and strategic guide to email deliverability. SPF, DKIM, DMARC setup, domain warm-up, sender reputation, and content best practices for cold outreach.
You wrote the perfect cold email. Your template is personalised, your CTA is compelling, and your ICP targeting is spot-on. But none of it matters if your email lands in spam. Deliverability is the invisible foundation of every email outreach campaign.
The Three Pillars of Deliverability
1. Domain Authentication (SPF, DKIM, DMARC)
These three DNS records prove to email providers that you're legitimate:
- SPF (Sender Policy Framework) — Lists which servers can send email from your domain
- DKIM (DomainKeys Identified Mail) — Adds a cryptographic signature to every email
- DMARC (Domain-based Message Authentication) — Tells providers what to do with unauthenticated emails
Without all three, major providers like Gmail and Outlook will flag your emails. Most email sending services like Resend guide you through setup in minutes.
2. Sender Reputation
Your domain and IP have a reputation score that email providers track. It's affected by:
- Bounce rate — Keep under 2%. Verify emails before sending.
- Spam complaints — Keep under 0.1%. Always include unsubscribe links.
- Engagement — Opens and replies improve your score. Targeting the right people matters.
3. Content Quality
Spam filters analyse your email content. Avoid:
- ALL CAPS in subject lines
- Excessive exclamation marks!!!
- Spammy words: "free", "guarantee", "act now", "limited time"
- Image-heavy emails with little text
- Shortened URLs (use full domain links)
Domain Warm-Up Strategy
New domains have zero reputation. You need to build it gradually:
- Week 1: Send 10-20 emails/day to people who will reply (colleagues, friends)
- Week 2: Increase to 30-50/day, mix in some cold outreach
- Week 3: Scale to 50-100/day if bounce rate stays under 2%
- Week 4+: Full volume, monitor daily
Using a Dedicated Outreach Domain
Never send cold email from your main company domain. If it gets blacklisted, your entire business email stops working. Instead, use a variant: if your company is acme.com, send cold email from try-acme.com or mail.acme.com.
Monitoring Deliverability
Tools like PerksMate's agent system track send events, bounces, and complaints automatically via the crm_lead_events table. Set alerts for bounce rates exceeding 2% or complaint rates above 0.1%.
Frequently Asked Questions
How long does domain warm-up take?+
Typically 2-4 weeks. Start with 10-20 emails/day to contacts who reply, then gradually increase. Don't rush it — a blacklisted domain takes months to recover.
Should I use my main domain for cold email?+
No. Always use a dedicated domain for outreach. If it gets flagged, your main business email remains unaffected. Use a similar variant like mail.yourdomain.com.
What bounce rate is too high?+
Keep it under 2%. Above 5% and email providers will start throttling or blocking your sends. Verify email addresses before sending to avoid bounces.
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