Deliverability Foundations
Authenticate all sending domains: SPF, DKIM, and DMARC — missing any one tanks deliverability
Warm up new domains/IPs: start with 50-100 emails/day, increase 20% daily over 2-4 weeks
Never buy email lists — purchased lists destroy sender reputation permanently
Clean list regularly: remove bounces immediately, unengaged after 90 days
Monitor blacklists: MXToolbox, Google Postmaster Tools — problems compound if not caught early
List Health Metrics
| Metric | Healthy | Warning | Critical |
|---|---|---|---|
| Open rate | >20% | 10-20% | <10% |
| Click rate | >2% | 1-2% | <1% |
| Bounce rate | <2% | 2-5% | >5% |
| Unsubscribe | <0.5% | 0.5-1% | >1% |
| Spam complaints | <0.1% | 0.1-0.3% | >0.3% |
- One spam complaint per 1000 emails is the danger zone — above this, inbox placement drops sharply
Subject Lines
40-50 characters optimal — truncates on mobile after 35-40
Personalization works: name or company in subject increases opens 10-20%
Curiosity beats clarity for opens, but clarity wins for clicks — balance based on goal
Avoid spam triggers: ALL CAPS, excessive punctuation!!!, "free", "act now"
Test emoji: works for some audiences, hurts others — A/B test before committing
Preview text is second subject line — don't waste it with "View in browser"
Email Sequences
Welcome sequence (5-7 emails over 2 weeks):
Immediate: Deliver promised value + set expectations
Day 1: Best content or quick win
Day 3: Story/origin + values
Day 5: Social proof + case study
Day 7: Soft offer or deeper engagement
Day 10: Address common objection
Day 14: Clear CTA
First email in sequence has highest open rate — make it count
Space emails 1-3 days apart — daily is too aggressive for most audiences
Segmentation
Segment by behavior, not just demographics — what they clicked matters more than job title
Minimum viable segments: new subscribers, engaged (opened in 30 days), unengaged, customers
Tag on every click — builds behavioral profile automatically
Sunset unengaged subscribers after 90 days — send re-engagement, then remove
VIP segment for highest engagement — reward them with early access, exclusives
Timing and Frequency
Tuesday-Thursday mid-morning performs best on average — but test your audience
B2B: business hours. B2C: evenings and weekends can work
Frequency depends on value: daily works if valuable, weekly fails if boring
Let subscribers choose frequency — reduces unsubscribes significantly
Send time optimization: most ESPs offer this, use it
Campaign Types
Newsletter: regular value, builds relationship, low direct conversion
Promotional: clear offer, urgency, direct conversion focus
Transactional: receipts, confirmations — highest open rates, add value here
Re-engagement: "We miss you" + incentive + easy unsubscribe
Announcement: product launches, major updates — segment to interested only
Writing for Email
One goal per email — multiple CTAs dilute response
Write for skimmers: bold key phrases, short paragraphs, bullet points
P.S. lines get read — put secondary CTA or key point there
Plain text often outperforms HTML for personal-style emails
Mobile-first: 60%+ open on mobile — single column, large tap targets
Automation Triggers
Sign up → Welcome sequence
Purchase → Onboarding + cross-sell sequence
Abandoned cart → 3-email recovery (1h, 24h, 72h)
No open in 30 days → Re-engagement sequence
Link click → Tag and trigger relevant follow-up
Date-based → Birthday, renewal reminder, anniversary
A/B Testing
Test one variable at a time: subject, send time, CTA, from name
Need 1000+ recipients per variant for statistical significance
Subject line tests: 20% of list first, winner to remaining 80%
Measure what matters: opens for subject, clicks for content, conversions for offers
Document every test — institutional learning prevents repeat experiments
Common Mistakes
Sending to entire list always — segment or face declining engagement
No double opt-in — leads to fake emails and spam traps
Ignoring mobile preview — broken layouts kill credibility
Same email to all segments — personalization is expected now
Hard selling too early — value first, offer later
Ignoring unsubscribe feedback — they tell you what's wrong
Compliance
Include physical address in every email — required by CAN-SPAM, GDPR
Unsubscribe must work within 10 days — one-click preferred
Honor opt-outs immediately — delayed removal is illegal in many jurisdictions
GDPR: explicit consent required, document it, allow data deletion
Separate consent for different email types — marketing vs transactional