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AI for Email Marketing Specialist

Use Klaviyo's Built-In AI for Subject Lines and Send Time Optimization

For Email Marketing Specialists

Tool: Klaviyo | AI Features: Subject Line AI, Smart Send Time | Time: 10 minutes to learn | Difficulty: Beginner

What This Does

Klaviyo has two built-in AI features that directly address the most time-consuming low-skill tasks in email marketing: writing subject line variants and choosing optimal send times. Both are included in paid Klaviyo accounts — no extra cost, no third-party tools.

Before You Start

  • You have a paid Klaviyo account (Core or above)
  • You're building or editing a campaign or flow email
  • You have at least one email built with subject line and content

Feature 1: AI Subject Line Generator

Steps

  1. In Klaviyo, open any campaign or flow email in the editor
  2. Navigate to the Subject line field
  3. Click the sparkle/AI icon next to the subject line input (appears when you focus the field)
  4. In the AI panel that opens, enter:
    • A brief description of what this email is about (2-3 sentences)
    • Your target audience (optional but improves results)
  5. Click Generate — Klaviyo returns 3-5 subject line options
  6. Click any option to insert it into the subject line field, or use as inspiration

What you should see: Subject line suggestions ranked by Klaviyo's predicted performance model, which is based on your account's historical open rate data and broader Klaviyo network data.

Troubleshooting: If the AI icon doesn't appear, check that you're in a campaign (not a draft template) and that your account has the feature enabled. Go to Account Settings → AI Features if you need to enable it.

Getting Better Results

  • The more specific your description, the better: "Re-engagement email for subscribers inactive for 60 days, offering a 15% comeback discount for a skincare brand" gets better results than "discount email"
  • Run the generator 2-3 times — each generation produces different options
  • Use the generated subject lines as starting points: copy one, open a ChatGPT tab, and ask for 5 variations on that angle

Feature 2: Smart Send Time

What It Does

Smart Send Time analyzes when your specific subscribers open emails and schedules each individual email to arrive at the time that person is most likely to engage — not a blanket "best time" for everyone.

Steps

  1. In a campaign, go to Schedule & Send (the final step before sending)
  2. Instead of choosing a manual send time, select Smart Send Time
  3. Klaviyo shows you a predicted lift vs. your current send time pattern
  4. Review the estimated improvement → click Schedule with Smart Send Time

What you should see: A delivery window (usually several hours) during which Klaviyo staggers delivery across your list based on each individual's engagement history. The campaign dashboard shows actual vs. expected open rates after send.

Minimum list size: Smart Send Time works best with 5,000+ active subscribers. Below that, there's insufficient personalization data.

Troubleshooting: If Smart Send Time is greyed out, your segment may be too small (under 500 contacts) or the feature may not be enabled for your plan. Check Klaviyo's pricing page for plan-specific feature availability.

Real Example

Without AI: You spend 20 minutes brainstorming subject lines for a Valentine's Day sale. You settle on "Valentine's Day Sale — 40% Off" because you're out of time. You schedule for 9am Tuesday because that's what you always do.

With Klaviyo AI:

  1. Click AI icon → describe email → get 5 options in 30 seconds: "Something to love at 40% off," "Treat yourself (or them) — sale ends Sunday," "Valentine's Day deal inside," "40% off: because you deserve it," "Last chance Valentine's savings"
  2. Pick "Treat yourself (or them) — sale ends Sunday" — it's warmer and more specific
  3. Enable Smart Send Time → Klaviyo delivers to each subscriber in their personal peak window
  4. Result: typically 2-4% open rate lift vs. static send time

Tips

  • A/B test the AI-suggested subject line against your own instinct — track which angle your specific audience responds to and use that to inform future writing
  • Use Smart Send Time for high-value campaigns (major sales, product launches) where open rate matters most; skip it for time-sensitive sends (flash sales ending in 2 hours) where you need immediate delivery
  • Check Klaviyo's predictive analytics dashboard monthly to see which send times are trending for your audience — use this to inform your manual scheduling when Smart Send Time isn't appropriate

Klaviyo features update regularly. If a feature has moved, look in the email editor's toolbar or Account → AI Features.