Email Design

Design high-converting marketing emails with AI-generated visuals via inference.sh CLI.

Quick Start

curl -fsSL https://cli.inference.sh | sh && infsh login
Generate email header banner
infsh app run infsh/html-to-image --input '{
  "html": "
Spring Sale — 30% Off
This weekend only
"
}'

> Install note: The install script only detects your OS/architecture, downloads the matching binary from dist.inference.sh, and verifies its SHA-256 checksum. No elevated permissions or background processes. Manual install & verification available.

Email Width & Layout

| Constraint | Value | Why | |-----------|-------|-----| | Max width | 600px | Gmail, Outlook rendering standard | | Mobile width | 320-414px | Responsive fallback | | Single column | Preferred | Better mobile rendering | | Two column | Use sparingly | Breaks on many clients | | Image width | 600px max, 300px for 2-col | Retina: provide 2x (1200px) | | Font size (body) | 14-16px | Below 14px is hard to read on mobile | | Font size (heading) | 22-28px | Must be scannable | | Line height | 1.5 | Readability on all devices |

The Inverted Pyramid Layout

The most effective email layout funnels attention to a single CTA:

┌──────────────────────────────────┐
│           HEADER IMAGE           │  ← Brand/visual hook
│          (600 x 200-300)         │
├──────────────────────────────────┤
│                                  │
│     Headline (one line)          │  ← What's this about
│                                  │
│     2-3 sentences of body copy   │  ← Why should I care
│     explaining the value.        │
│                                  │
│        ┌──────────────┐          │
│        │   CTA BUTTON  │         │  ← One clear action
│        └──────────────┘          │
│                                  │
├──────────────────────────────────┤
│     Footer: Unsubscribe link     │
└──────────────────────────────────┘

Subject Lines

Formulas That Work

| Formula | Example | Open Rate Impact | |---------|---------|-----------------| | Number + benefit | "5 ways to cut your build time in half" | High | | Question | "Are you still deploying on Fridays?" | High | | How-to | "How to automate your reports in 3 steps" | Medium-High | | Urgency (genuine) | "Last day: 30% off annual plans" | High (if real) | | Personalized | "[Name], your weekly report is ready" | Very High | | Curiosity gap | "The one feature our users can't stop talking about" | Medium-High |

Rules

| Rule | Value | |------|-------| | Length | 30-50 characters (mobile truncates at ~35) | | Preview text | First 40-100 chars after subject — design this intentionally | | Emoji | Max 1, at start or end, test with your audience | | ALL CAPS | Never — triggers spam filters | | Spam trigger words | Avoid: "free", "act now", "limited time", "click here" in subject | | Personalization | [First name] in subject lifts open rates 20%+ |

Preview Text

The preview text appears after the subject line in the inbox. Don't waste it.

❌ "View this email in your browser" (default, wasted space)
❌ "Having trouble viewing this?" (no one cares)
✅ Subject: "5 ways to cut build time"
   Preview: "Number 3 saved us 6 hours per week"
✅ Subject: "Your monthly report is ready"
   Preview: "Revenue up 23% — here's what drove it"

Email Types

Welcome Email (Automated, Day 0)

| Element | Content | |---------|---------| | Subject | "Welcome to [Product] — here's what's next" | | Header | Brand image or product screenshot | | Body | 3-4 sentences: what they signed up for, what to expect, one quick win | | CTA | "Complete your setup" or "Try your first [action]" | | Timing | Immediately after signup |

Promotional / Campaign

| Element | Content | |---------|---------| | Subject | Benefit-focused, urgency if real | | Header | Hero image showing the offer/outcome | | Body | Problem → solution → offer → deadline | | CTA | "Get 30% Off" or "Start Free Trial" | | Urgency | Real deadline, not fake scarcity |

Product Update / Changelog

| Element | Content | |---------|---------| | Subject | "New: [Feature name] is here" | | Header | Screenshot or visual of the feature | | Body | What's new, why it matters, how to use it | | CTA | "Try [feature]" |

Transactional (Receipts, Confirmations)

| Rule | Why | |------|-----| | Clear purpose in subject | "Your order #1234 is confirmed" | | Minimal design | Don't confuse with marketing | | Key info above the fold | Order number, amount, date | | No promotional content (mostly) | CAN-SPAM allows some, but keep minimal |

Header Image Design

# Welcome email header
infsh app run infsh/html-to-image --input '{
  "html": "
Welcome to
DataFlow
Your data, automated
"
}'
Sale / promotional header
infsh app run infsh/html-to-image --input '{
  "html": "
This Weekend Only
30% OFF
All annual plans. Ends Sunday.
"
}'
Feature announcement header with AI visual
infsh app run falai/flux-dev-lora --input '{
  "prompt": "clean modern email header banner, abstract flowing data visualization, dark blue gradient background, subtle glowing nodes and connections, tech aesthetic, minimal, no text, 600x250 equivalent",
  "width": 1200,
  "height": 500
}'

CTA Buttons

| Rule | Value | |------|-------| | Width | 200-300px, not full width | | Height | 44-50px minimum (tap target) | | Color | High contrast with background | | Text | Action verb + outcome: "Start Free Trial" | | Shape | Rounded corners (4-8px border-radius) | | Placement | Above the fold, repeated at bottom for long emails | | Quantity | ONE primary CTA per email |

Bulletproof Buttons

HTML buttons render differently across email clients. Use the "bulletproof button" technique (VML for Outlook, HTML/CSS for everything else):

  

    

      
        Start Free Trial
      
    
  

Mobile Optimization

| Rule | Why | |------|-----| | Single column layout | Multi-column breaks on mobile | | Font minimum 14px | Smaller is unreadable | | CTA button minimum 44px tall | Apple/Android tap target | | Images scale to 100% width | Prevent horizontal scroll | | Stack elements vertically | Side-by-side breaks on narrow screens | | Test on Gmail app, Apple Mail, Outlook | The big 3 email clients |

60%+ of emails are opened on mobile. Design mobile-first.

Deliverability Checklist

| Factor | Rule | |--------|------| | Image-to-text ratio | Max 40% images, 60% text (spam filters flag image-heavy emails) | | Alt text on images | Always — images blocked by default in many clients | | Unsubscribe link | Required by law (CAN-SPAM, GDPR) — make it easy to find | | From name | Recognizable person or brand name | | Reply-to | Real address, not no-reply@ (hurts deliverability) | | List hygiene | Remove bounces, clean inactive subscribers quarterly | | SPF/DKIM/DMARC | Technical authentication — set up once, critical for inbox |

Common Mistakes

| Mistake | Problem | Fix | |---------|---------|-----| | No preview text | Shows "View in browser" or random code | Set preview text intentionally | | Image-only emails | Blocked images = blank email + spam risk | 60%+ text, alt text on images | | Multiple CTAs | Decision paralysis, lower click rate | One primary CTA per email | | Tiny text | Unreadable on mobile | Minimum 14px body, 22px headings | | no-reply@ sender | Hurts deliverability, feels impersonal | Use real reply address | | No mobile testing | Broken layout for 60%+ of readers | Test on Gmail app + Apple Mail | | Missing unsubscribe | Illegal (CAN-SPAM) + spam complaints | Clear unsubscribe link in footer | | Over-designing | Email clients render CSS inconsistently | Simple layouts, inline styles | | Fake urgency | Erodes trust, trains users to ignore | Only use real deadlines |

Related Skills

npx skills add inference-sh/skills@landing-page-design
npx skills add inference-sh/skills@ai-image-generation
npx skills add inference-sh/skills@prompt-engineering

Browse all apps: infsh app list

curl -fsSL https://cli.inference.sh | sh && infsh login
Generate email header banner
infsh app run infsh/html-to-image --input '{
  "html": "
Spring Sale — 30% Off
This weekend only
"
}'

> Install note: The install script only detects your OS/architecture, downloads the matching binary from dist.inference.sh, and verifies its SHA-256 checksum. No elevated permissions or background processes. Manual install & verification available.

| Rule | Value | |------|-------| | Length | 30-50 characters (mobile truncates at ~35) | | Preview text | First 40-100 chars after subject — design this intentionally | | Emoji | Max 1, at start or end, test with your audience | | ALL CAPS | Never — triggers spam filters | | Spam trigger words | Avoid: "free", "act now", "limited time", "click here" in subject | | Personalization | [First name] in subject lifts open rates 20%+ |

Preview Text

The preview text appears after the subject line in the inbox. Don't waste it.

❌ "View this email in your browser" (default, wasted space)
❌ "Having trouble viewing this?" (no one cares)
✅ Subject: "5 ways to cut build time"
   Preview: "Number 3 saved us 6 hours per week"
✅ Subject: "Your monthly report is ready"
   Preview: "Revenue up 23% — here's what drove it"