Email Deliverability & Domain Warmup: The Complete Guide
How to warm up a new sending domain, maintain sender reputation, and ensure your emails land in the inbox. Includes SPF, DKIM, DMARC setup.
Why Deliverability Matters
You can write the best emails in the world, but if they land in spam, none of it matters.
| Problem | Impact |
|---|---|
| 10% inbox drop | ~10% revenue loss |
| Spam folder | 95%+ never get read |
| Blacklisting | Can't reach subscribers |
| Damaged reputation | 4-8 weeks to recover |
Four Factors That Determine Inbox Placement
Sender Reputation — Your track record with email providers. Built over time through consistent, engaged sending.
Email Authentication — SPF, DKIM, DMARC records that verify you're authorized to send from your domain.
List Quality — Engagement rates, bounce rates, spam complaints. Low engagement = deliverability problems.
Content — Spam trigger words, formatting, HTML quality. Less important than reputation but still matters.
Email Authentication Setup
Configure these before sending any marketing email:
SPF (Sender Policy Framework)
Tells receiving servers which IPs can send on your behalf.
Type: TXT
Host: @
Value: v=spf1 include:klaviyo.com ~all
DKIM (DomainKeys Identified Mail)
Adds a digital signature verifying emails haven't been tampered with.
Type: CNAME
Host: k1._domainkey
Value: dkim.klaviyo.com
DMARC (Domain-based Message Authentication)
Tells servers what to do if authentication fails. Start with monitoring.
Type: TXT
Host: _dmarc
Value: v=DMARC1; p=none; rua=mailto:dmarc@yourdomain.com
Domain Warmup Schedule
New domain or significantly increased volume? You must warm up gradually. Skipping warmup lands you in spam.
Do not skip warmup. High volume from a new domain immediately will land you in spam, and recovery takes 4-8 weeks.
Warmup Monitoring
| Metric | Target | Red Flag |
|---|---|---|
| Open Rate | 40%+ | Below 25% |
| Click Rate | 5%+ | Below 2% |
| Bounce Rate | Under 0.5% | Above 2% |
| Spam Complaints | Under 0.05% | Above 0.1% |
Ongoing Best Practices
List Hygiene:
- Remove hard bounces (automatic in most ESPs)
- Suppress 180+ day inactive quarterly
- Verify imported lists before import
Engagement Management:
- Segment by engagement level
- Make unsubscribe easy
- Monitor complaint rates (under 0.1%)
- Send relevant content
Content:
- Avoid spam triggers ("FREE!!!", excessive caps)
- Good text-to-image ratio
- Include plain text version
- Consistent "From" name
Recovery Plan
Already in spam? Follow this:
Week 1: Stop the Bleeding
- Pause all campaigns
- 30-day engaged only
- Reduce to 500-1,000 daily
Week 2: Clean the List
- Remove 90+ day inactive
- Run list through verification (NeverBounce, ZeroBounce)
Weeks 3-6: Re-Warmup
- Follow warmup schedule above
- Start with most engaged 500-1,000
- Only scale if metrics stay healthy
Ongoing: Monitor
- Check Google Postmaster daily
- Watch every send's open rate
- Don't rush — patience essential
Essential Monitoring Tools
Google Postmaster Tools (Free) — See how Gmail views your domain, spam rate, reputation.
Your ESP Analytics — Open rates, bounces, spam complaints.
MXToolbox (Free) — Blacklist status, authentication verification.
Dedicated vs. Shared Domain
- No warmup required
- Easier setup
- Reputation tied to others
- Good for lower volumes
- Full control over reputation
- Requires 4-6 week warmup
- More technical setup
- Better for 50,000+/month
Checklist
One-Time Setup:
- SPF record configured
- DKIM record configured
- DMARC record configured
- Custom sending domain (if applicable)
- Google Postmaster connected
Ongoing:
- Monitor open rates weekly
- Check spam complaints weekly
- Review Google Postmaster monthly
- Clean inactive quarterly
- Check blacklist monthly
Get Expert Help
Deliverability issues cost significant revenue. We diagnose and fix deliverability problems as part of our retention services.
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