Use this skill when designing email campaigns, building drip sequences, improving deliverability, or A/B testing email content. Triggers on email campaigns, drip sequences, newsletter, email deliverability, subject lines, email automation, segmentation, open rates, click-through rates, and any task requiring email marketing strategy or execution.
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Use this skill when designing email campaigns, building drip sequences, improving deliverability, or A/B testing email content. Triggers on email campaigns, drip sequences, newsletter, email deliverability, subject lines, email automation, segmentation, open rates, click-through rates, and any task requiring email marketing strategy or execution.
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Email Marketing
Email marketing remains one of the highest-ROI channels in digital marketing
(average $36 for every $1 spent). Effective email marketing is not about sending
more emails - it is about sending the right message to the right person at the
right time. This skill covers campaign design, drip sequence architecture,
deliverability fundamentals, segmentation models, and systematic A/B testing.
When to use this skill
Trigger this skill when the user:
Wants to design or improve an email campaign (newsletter, promotional, announcement)
Needs to build a drip sequence (welcome series, onboarding, nurture, re-engagement)
Asks about email deliverability, spam scores, or inbox placement
Wants to write or improve subject lines or preview text
Needs to set up email automation flows and triggers
Asks about audience segmentation strategies
Wants to run A/B tests on email content or timing
Needs to understand or improve open rates, CTR, or conversion rates
Asks about responsive / mobile email design
Wants to set up lifecycle email automation
Do NOT trigger this skill for:
SMS or push notification marketing (different channel mechanics)
Cold outbound sales prospecting (governed by separate compliance frameworks
like CAN-SPAM / GDPR and different deliverability rules than permission email)
Key principles
Permission-based always - Only email people who explicitly opted in.
Purchased lists destroy sender reputation, violate GDPR/CAN-SPAM, and produce
near-zero ROI. A small engaged list beats a large unengaged one every time.
Segment before sending - A single blast to your entire list is almost never
the right move. Even basic segmentation (active vs. dormant, product interest,
lifecycle stage) meaningfully improves relevance and reduces unsubscribes.
Subject line is 80% of the battle - If the email is not opened it does not
exist. Spend disproportionate effort on subject lines and preview text. Test
them constantly.
Mobile-first design - More than 60% of emails are opened on mobile.
Single-column layouts, minimum 16px body text, large tap targets (44px+),
and short subject lines (under 40 characters) are non-negotiable defaults.
Test everything - Intuition about what works in email is frequently wrong.
Run structured A/B tests on subject lines, CTAs, send times, and content
format. Let data override opinion.
Transactional emails have the highest open rates (60-80%) and must not be used
for marketing purposes - doing so violates trust and often CAN-SPAM.
Deliverability factors
Deliverability is whether your email reaches the inbox (not just whether it was
"sent"). Key factors:
Sender reputation - ISPs score your sending domain and IP based on engagement,
spam complaints, and bounce rates. Reputation takes months to build and days to
destroy. Keep complaint rates below 0.1% and hard bounce rates below 2%.
Authentication - Three DNS records that ISPs use to verify you are who you
say you are:
SPF (Sender Policy Framework) - lists authorized sending IPs for your domain
DKIM (DomainKeys Identified Mail) - cryptographically signs each email
DMARC (Domain-based Message Authentication) - policy for handling failures;
start with p=none (monitor), progress to p=quarantine, then p=reject
List hygiene - Remove hard bounces immediately. Suppress unsubscribes
immediately. Run re-engagement campaigns before sunsetting inactive subscribers.
Engagement signals - Opens, clicks, and replies positively signal to ISPs.
Low engagement from a segment drags down your domain reputation. Suppress
chronically unengaged subscribers.
Segmentation models
Model
Segments
When to use
Engagement-based
Active, At-risk, Dormant
Deliverability management, re-engagement
Lifecycle stage
Prospect, New customer, Loyal, Lapsed
Onboarding and retention flows
RFM
Recency, Frequency, Monetary
E-commerce, purchase-based personalization
Behavioral
Pages visited, features used, content downloaded
SaaS onboarding, content marketing
Demographic
Role, company size, industry
B2B campaigns, product-specific content
Key metrics
Metric
Definition
Healthy benchmark
Open rate
Unique opens / emails delivered
20-30% (B2C), 25-35% (B2B)
Click-through rate (CTR)
Unique clicks / emails delivered
2-5%
Click-to-open rate (CTOR)
Clicks / opens - measures content quality
10-20%
Conversion rate
Desired actions / emails delivered
Varies by goal
Unsubscribe rate
Unsubs / emails delivered
Keep below 0.2%
Spam complaint rate
Complaints / emails delivered
Keep below 0.1%
Hard bounce rate
Permanent delivery failures / sent
Keep below 2%
Note: Apple Mail Privacy Protection (MPP) inflates open rates since iOS 15.
Use CTOR and conversion rate as more reliable engagement signals.
Common tasks
Design a drip sequence
A drip sequence is a series of pre-written emails sent on a schedule or triggered
by behavior. Plan before writing:
Define the goal - What behavior should the sequence drive? (activation,
purchase, re-engagement, education)
Map the journey - What does the subscriber need to know / feel / do at each
step to move toward the goal?
Set timing - Welcome: immediate. Onboarding: days 0, 2, 5, 10. Nurture:
weekly or bi-weekly. Re-engagement: day 30, 45, 60 of inactivity.
Write each email as a unit - Each email should have one goal, one CTA.
Ready-to-use templates for welcome, onboarding, and nurture sequences:
see references/drip-templates.md.
Welcome series structure (3 emails):
Email 1 (immediate): Deliver the promised value, set expectations, introduce brand
Email 2 (day 2-3): Share your best piece of content or biggest benefit
Email 3 (day 5-7): Social proof + primary CTA
Onboarding series structure (5 emails):
Email 1 (day 0): Account created - first action to take (one thing only)
Email 2 (day 2): How to accomplish the primary use case
Email 3 (day 5): Advanced tip or power feature
Email 4 (day 10): Success story from a similar user
Email 5 (day 14): Check-in - did they reach activation? If not, offer help.
Nurture series structure:
Value-first ratio: 3 educational emails for every 1 promotional email
Frequency: 1-2 per week maximum; let engagement guide cadence
Personalize based on content topic interest or product category
Write high-converting subject lines
Subject lines determine whether the email gets opened. Apply these formulas:
Formula
Template
Example
Curiosity gap
"[Intriguing claim] (here's why)"
"We almost didn't send this email"
Numbered list
"[N] ways to [achieve outcome]"
"5 ways to cut your churn in half"
Direct benefit
"[Outcome] in [timeframe/way]"
"Double your open rates this week"
Question
"[Question the reader is asking themselves]"
"Still struggling with deliverability?"
Social proof
"How [person/company] achieved [result]"
"How Notion grew to 20M users via email"
Urgency/scarcity
"[Benefit] - [deadline]"
"Your free trial ends tomorrow"
Personalization
"[First name], [relevant message]"
"Sarah, your report is ready"
Subject line rules:
Keep under 50 characters (under 30 for mobile previews)
Avoid ALL CAPS, excessive punctuation, and spam trigger words (free!!!, act now)
Preview text is the second subject line - write it intentionally (120-150 chars)
Never deceive - a misleading subject line increases complaints and unsubscribes
A/B test every subject line on a 20% sample before sending to full list
Build email segmentation strategy
Audit existing data - What do you actually have? (email, name, signup source,
purchase history, behavioral events, custom attributes)
Define your segments - Start with 3-5 meaningful segments, not 20 micro-segments
Map content to segments - What does each segment need from you?
Set up suppression rules - Who should never receive this campaign type?
Plan re-entry criteria - When does someone move from one segment to another?
Minimum viable segmentation for most businesses:
Active subscribers (opened or clicked in last 90 days)
At-risk subscribers (no engagement in 90-180 days)
Dormant subscribers (no engagement 180+ days) - run re-engagement or suppress
A/B test email campaigns
Test one variable at a time. Common elements to test in priority order:
Element
What to test
Minimum sample size
Subject line
Length, question vs. statement, personalization
1,000 per variant
From name
Brand name vs. person name vs. "Name at Brand"
1,000 per variant
Send time
Day of week, time of day
2,000 per variant
CTA button
Text, color, placement, count
2,000 per variant
Email length
Short (150-300 words) vs. long (500+ words)
2,000 per variant
Personalization
Generic vs. first name vs. behavior-based
2,000 per variant
A/B test process:
Form a hypothesis: "Personalized subject lines will increase open rate by 5%"
Split list randomly (not by time - that introduces bias)
Send simultaneously or within a 1-hour window
Wait for statistical significance (95% confidence, typically 24-48h)
Document result in a test log; apply winner to full list
Apply learning to future tests
Improve deliverability
Step 1 - Authenticate your domain (critical baseline):
# SPF record (TXT record on your domain)
v=spf1 include:sendgrid.net include:mailchimp.com ~all
# DKIM - generated by your ESP, looks like:
mail._domainkey.yourdomain.com TXT "v=DKIM1; k=rsa; p=<public-key>"
# DMARC record
_dmarc.yourdomain.com TXT "v=DMARC1; p=none; rua=mailto:dmarc@yourdomain.com"
Progress DMARC policy from p=none to p=quarantine to p=reject over 60-90
days as you verify all legitimate sending sources are authenticated.
Step 2 - Warm up new sending IPs:
Week 1: 200-500 emails/day to your most engaged subscribers
Week 2: 1,000-2,000/day
Week 3-4: Double weekly until at target volume
Never jump more than 2x volume day-over-day
Step 3 - Maintain list hygiene:
Remove hard bounces immediately after every send
Suppress unsubscribes within 10 business days (CAN-SPAM) / immediately (GDPR)
Sunset subscribers with zero engagement after 6-12 months
Use double opt-in to improve list quality at source
Step 4 - Monitor reputation:
Google Postmaster Tools - monitor spam rate and domain reputation
Microsoft SNDS - equivalent for Outlook/Hotmail
MXToolbox - check blacklist status
Design responsive email templates
Email clients are fragmented - Outlook uses a Word rendering engine; Gmail clips
emails over 102KB. Design for the lowest common denominator.
HTML email best practices:
Use table-based layouts for maximum compatibility (CSS grid/flexbox fail in Outlook)
Inline all CSS - many clients strip <style> blocks
Single-column layout, 600px max width
16px minimum body font size; 22px+ for headlines
Preheader text in a hidden <div> immediately after <body>
Always include a plain-text version
Images must have alt text; emails must render acceptably with images off
CTA buttons built with HTML/CSS, not images
Test in Litmus or Email on Acid before sending
Mobile-specific rules:
Tap targets minimum 44x44px
Short subject lines (under 30 chars show on most lock screens)
Stack multi-column layouts to single column on mobile via media query
Use system fonts (Arial, Georgia, Verdana) as fallbacks
Set up lifecycle email automation
Lifecycle automation sends the right message triggered by user behavior, not a
calendar.
Core triggers and flows:
Trigger
Flow
Emails
Signup
Welcome series
3-5 emails over 1-2 weeks
First purchase
Post-purchase onboarding
Thank you, how-to, cross-sell at day 7
Trial started
Activation sequence
Feature highlights, success tips, upgrade prompt
Feature not used
Feature education
1-2 targeted tips emails
Inactivity (30 days)
Re-engagement
"We miss you" + incentive
Inactivity (60 days)
Win-back
Final offer + unsubscribe prompt
Cart abandonment
Recovery flow
Email at 1h, 24h, 72h
Purchase anniversary
Loyalty / retention
Thank you + relevant upsell
Automation setup checklist:
Define entry trigger (event, date, list membership change)
Set enrollment conditions (prevent duplicate enrollment)
Map the email sequence with delays
Set exit criteria (purchased, unsubscribed, became customer)
Add goal tracking to measure conversion
Review and prune flows quarterly
Anti-patterns / common mistakes
Mistake
Why it's wrong
What to do instead
Emailing a purchased or scraped list
Destroys sender reputation, violates GDPR/CAN-SPAM, near-zero ROI
Only email people who explicitly opted in to your list
Sending the same email to your entire list
Irrelevant content drives unsubscribes and spam complaints
Segment by lifecycle stage or engagement level before sending
Using misleading subject lines ("clickbait")
Increases complaint rate; damages brand trust even if open rate spikes
Write subject lines that accurately reflect email content
Ignoring hard bounces
Accumulating bounces tanks sender reputation
Remove hard bounces immediately after each send
Sending at maximum volume from a new IP or domain
ISPs rate-limit and blacklist sudden high-volume senders
Warm up IP/domain over 4-6 weeks with gradual volume ramp
Testing multiple variables simultaneously
Cannot attribute results to a single cause
Test one variable at a time with proper control and variant groups
Gotchas
Apple Mail Privacy Protection inflates open rates since iOS 15 - open rate alone is no longer a reliable metric - Apple pre-fetches email content to load tracking pixels, registering an "open" even when the user never read the email. Use click-to-open rate (CTOR) and conversion rate as primary engagement signals. Open rate is still useful for trend analysis but not absolute benchmarking.
Outlook renders email using the Word rendering engine, not a browser - CSS flexbox, grid, and many modern properties silently fail in Outlook. Table-based HTML layouts with inlined CSS are still required for reliable Outlook rendering. Always test in Litmus or Email on Acid before sending to a list that includes corporate Outlook users.
Gmail clips emails over 102KB of HTML - A clipped email shows a "View entire message" link, hiding your CTA, footer unsubscribe link, and often breaking rendering entirely. Keep HTML under 102KB. Heavy templates with extensive inline CSS are the most common culprit.
Sending re-engagement campaigns to your entire dormant segment at once can trigger blocklisting - Dormant subscribers who haven't engaged in 6+ months are higher spam-complaint risk. Splitting re-engagement sends into smaller daily batches reduces the risk of a complaint spike that harms your domain reputation for active subscribers.
A/B tests on small lists produce statistically meaningless results - Running a subject line test on 200 subscribers with a 50/50 split gives 100 per variant - nowhere near the 1,000 minimum needed for reliable signal. Shipping the "winner" from an underpowered test is often worse than just picking one option.
References
For detailed templates and ready-to-use content, read:
references/drip-templates.md - Complete drip sequence templates for welcome,
onboarding, nurture, and re-engagement flows
Only load the references file when the current task requires ready-to-use
template content or detailed sequence copy.
Companion check
On first activation of this skill in a conversation: check which companion skills are installed by running ls ~/.claude/skills/ ~/.agent/skills/ ~/.agents/skills/ .claude/skills/ .agent/skills/ .agents/skills/ 2>/dev/null. Compare the results against the recommended_skills field in this file's frontmatter. For any that are missing, mention them once and offer to install:
