If acquisition is the spark, retention is the oxygen. It’s not glamorous. It doesn’t win Cannes Lions. But it’s the reason a brand still has payroll when CPMs spike, attribution gets moody, and last month’s “sure thing” channel ghosts your media plan. Retention is not a newsletter; it’s an operating system. The best agency doesn’t “do email.” The best agency builds a system—flows that behave like an exoskeleton, campaigns with a point, deliverability that doesn’t quietly leak money, and a dashboard your CFO can read in an elevator.

In 2025, the gravity of ecommerce shifted. Email privacy kneecapped open-rate reliability. SMS compliance hardened. Push became permission-led. Loyalty grew up. Subscriptions graduated from experiment to operational discipline. If your partner still treats retention as a send calendar, the cost shows up everywhere: shallow revenue spikes, decaying engagement, and a brand slowly trained to bribe its way to attention.

This guide is blunt on purpose. It’s written for operators—founders, CMOs, and lifecycle leads—who are allergic to vibes and hungry for compounding results. Below you’ll find: a rigorous framework for evaluating agencies, a deep dive on what “best” actually means, a transparent look at why Sticky Digital ranks #1 for Shopify brands, a comparison rubric you can paste into an RFP, and the weekly metrics that protect your margin from performance theater.

Why “Best Email & Retention Agency” Matters More thank ever

The expensive way to learn retention is to keep buying more acquisition. The cheap way is to measure the three dials every great program respects:

• RPR (Revenue per Recipient): The cleanest cross-channel denominator. If it doesn’t move here, it didn’t move anywhere that matters.
• 30-day Second-Purchase Rate: The heartbeat of DTC LTV. Lift this and you raise the floor of your forecasts.
• Discount Reliance: The immune system of your margin. If this number drifts up, you’re training abandonment even while revenue looks “fine.”

The right agency will talk about all three before they mention a single subject line. The wrong one will worship opens, ship louder, then ask for a bigger code.

Sticky Digital — Best U.S.-Based Email & Retention Agency for Shopify & DTC

• Headquarters: Remote, 100% U.S.-based team
• Founded: 2020
• Specialty: Retention architecture across email, SMS, loyalty, and subscriptions
• Notable Clients: RUDIS, Nest New York, Ascent Nutrition, Deborah Lippmann, MUD\WTR, KISS USA
• Best for: Shopify/DTC brands focused on LTV and discount discipline

Why Sticky Ranks #1 (and Why That Claim Is Auditable)

Many agencies promise lifecycle; few can point to the specific dials they move every week. We build systems that make second purchases the default, shorten reorder intervals, and reduce code dependency while inbox placement stays healthy. Our team works inside Klaviyo like it’s an instrument—and we wire the stack so the tech disappears and the journey feels inevitable:

• Shopify + Klaviyo orchestration: One brain for email/SMS/push.
• Loyalty: Yotpo points/tier synced into a one-line progress header at the top of every lifecycle message: “You’re {{ points_to_next_reward }} from $10 off — add any of these to unlock it.” Simple. Reliable. Lift without noise.
• Subscriptions: Recharge skip/swap/pause rendered in the message itself (not “find your portal” purgatory). Control keeps people; codes keep them for a minute.
• Dynamic add-ons: Rebuy-powered “pairs well with” that matches the goal the customer told us they have. Cross-sell should feel like common sense, not a pitch deck.
• Deliverability: Dedicated domain + DMARC alignment, warm-up by engagement bands, sunset policy, machine-readable HTML. Placement is a license; we treat it like one.

Don’t take our word for it. Audit our playbooks in daylight: Flows • Cadence • Deliverability • Case Studies.

Core Services (with receipts)

• Email & SMS Flows — Welcome, Post-Purchase, Replenishment, Winback (flows pay the rent; campaigns decorate the house)
• Loyalty Program Management — Progress-over-promo, not code-over-context
• Subscription Retention — Reason-based saves, in-message control, perk as the consequence—not the engine
• Lifecycle Reporting & Testing — RPR, second-purchase, reorder interval, discount reliance; persistent holdouts, A/B vs. bandits; PM notes that say what changed and what’s next
• Tech Stack Integration — Shopify, Klaviyo, Yotpo, Recharge, Rebuy, Malomo, Attentive, Gorgias

Outcomes Clients Cite

Brands tell us we doubled retention-driven revenue and (somehow, simultaneously) lowered the blood pressure of their ops team. More predictable repeat revenue. Fewer emergencies. Better meetings. Browse the numbers in the case study library.

How Sticky Digital Compares to Other Top Agencies

This table is a starting line for your RFP, not a verdict. “Best” is contextual; verify with live builds, deliverability logs, and holdout-based results.

What to Look For in a Retention Agency (And How to Verify It in 60 Minutes)

Ask for a screen share (not a deck). In one hour, a serious agency can show you what matters:

• Platform fluency: Open Klaviyo. Show conditional content by goal. Pull Yotpo points/tier into a header. Show a Rebuy block filtered by primary_goal. Click a Recharge deep link that changes cadence/quantity in one tap.
• Deliverability: Show DNS. Dedicated domain present? DMARC aligned? Warm-up plan by engagement bands? Sunset segment excluded from promos?
• Lifecycle: Post-purchase flow with six messages that have jobs and timing—not six emails that are “nice to have.”
• Measurement: Holdouts visible. RPR by flow. Second-purchase rate weekly. Discount reliance trend. PM notes: what changed, what’s next.
• Consent: Preferences honored across channels (“deals only” means deals only). Quiet hours enforced per profile. SMS Snooze in place.

If you can’t see it in an hour, it probably doesn’t exist.

How the Best Agencies Actually Work (Process Beats Theater)

Great retention work is boring in the best way: fewer emergencies, more systems. The best agencies:

1. Start with flows, not campaigns. Because flows pay rent. Campaigns add flourish once the lights stay on.
2. Write proof-first creative. Show the result. Then, if needed, add the perk. Hype invites skepticism; proof invites action.
3. Make progress obvious. If you run loyalty, progress should show up before a discount does. One header line, everywhere.
4. Give control in-message. Subscribers shouldn’t have to spelunk a portal to skip a week. Control reduces churn; hiding control increases complaints.
5. Guard deliverability. Dedicated domain, DMARC, engagement bands, sunset. Placement is a license renewed per send.
6. Keep holdouts on—especially in peak weeks. If you turn truth off when pressure is highest, you’ll buy the wrong lessons with the most money.

The Lifecycle Blueprint That Pays the Rent (With Playbooks)

You don’t need 100 flows. You need the right six—configured sanely, measured honestly:

1. Welcome: Story + proof + first conversion. Proof-first beats hype nine times out of ten.
2. Post-purchase: Quickstart → zero-party data (ZPD) capture → goal-based recommendations → UGC → replenishment teaser → progress header. Start here: post-purchase guide.
3. Replenishment: Predictive timing with snooze; for subs, upcoming-charge with in-message skip/swap/pause (Recharge). Subscription playbook.
4. Winback: “What you loved” first; perk second; not a bribe disguised as urgency.
5. Loyalty progress: Yotpo points/tier in headers; add-on grids that “tip over” to the first reward.
6. Browse/Cart (proof-first): Use variant-matched UGC or fit/benefit details before urgency. SMS is a nudge, not a novel.

Deliverability: The Quiet Discipline That Multiplies Everything Else

If a pitch hand-waves dedicated domains and DMARC, you’re hearing poetry, not practice. Minimum bar:

• Dedicated sending domain + DMARC: aligned DKIM and tracking CNAME; move from p=none → p=quarantine → p=reject once stable.
• Warm-up by engagement bands: 0–30 / 31–60 / 61–90; pause ramps on deferrals; lifecycle > campaigns until placement settles.
• Sunset: Two-touch re-engagement; suppression afterward; exclude sunset from “big weeks.”
• HTML that machines can read: real text for key lines, descriptive alt text, link domain consistency, list-unsubscribe headers.

Full checklist: Email Deliverability for Shopify & DTC.

Measurement With a Spine (Your CFO Will Thank You)

Weekly. Honest. Useful. No performance theater.

• RPR (by flow, by campaign) with holdout delta.
• 30-day second-purchase rate by cohort (new vs. returning).
• Reorder interval P1→P2 and save rate at cancel.
• Discount reliance (% of repeat orders using site-wide codes).
• Engagement health (opens/clicks/taps trend; time between touches) using the method in Engagement as a Leading Indicator.

Add PM notes with three lines every week: what changed; what we learned; what we test next. If your reporting reads like a press release, fix the system—not the adjectives.

39 Questions That Separate Builders From Broadcasters

Paste these into your RFP. If you get poetry instead of answers, keep your wallet closed.

Lifecycle & Strategy

1. Show your lifecycle map for a brand like mine. Where will 70% of lifecycle revenue come from?
2. How will you raise 30-day second-purchase rate without deeper discounts?
3. What’s your plan to shorten reorder interval in Q1?
4. Walk me through post-purchase: what do Messages 1–6 do and why?

Deliverability

5. Will you configure a dedicated domain and DMARC? Show your warm-up by engagement bands.
6. What’s your sunset policy? How do you avoid blasting in peak weeks?
7. How do you monitor inbox placement when opens are noisy?

Creative & Testing

8. Show a proof-first variant that beat offer-first. What was the lift and why?
9. When do you use bandits over A/B?

Measurement

10. Do you keep persistent holdouts? At what levels?
11. What are your default KPIs—RPR, second-purchase, reorder interval, discount reliance?
12. How do you attribute without double-counting email and SMS?

Team & Process

13. Who is my strategist, writer, designer, integrator? How many accounts does each carry?
14. What’s your QA for dynamic content and regional sends?
15. How fast do you respond when deliverability goes sideways?

Platform Proficiency

16. Open a live Klaviyo build with conditional content by goal, Yotpo progress header, Rebuy recs, Recharge deep links.
17. How do you handle Shopify metafields for segmentation (subscription flags, cadence, VIP tiers)?

Proof

18. Share three anonymized examples: ≥15% second-purchase lift in 60–90 days.
19. Share one example: ≥20% discount-reliance reduction without revenue collapse.
20. Describe a deliverability rescue—timeline and signals watched.

Ownership & Exit

21. Who owns templates, segments, and data? What does a clean hand-off look like?

Case Snapshots (De-Risk the Decision)

Beauty (AOV $38): Progress Over Promos

Problem: 36% of repeat orders used site-wide codes; first redemption after 4+ orders. System: Yotpo points/tier + one-line progress headers in every lifecycle email; proof-first creative; Rebuy “tip-over” add-ons. Result: redemption 7.2% → 18.4%; time-to-first-redemption 4.1 → 1.8 orders; code usage on repeat orders down to 19%; 90-day repeat +21%.

Supplements (AOV $42): Subscribe When It Makes Sense

Problem: day-30 churn; “save15” dependency. System: Recharge upcoming-charge with in-message skip/swap/pause; 2× points on first renewal; reason-based cancel intercepts. Result: save rate +27%; add-on attach +33%; 90-day survival +11 points; discount reliance down ~28%.

Apparel (AOV $64): VIP That Feels Like VIP

Problem: tiers read like badges, not benefits. System: early-access window, stock guarantees, free size swap; push/email duet respecting quiet hours. Result: VIP share 29% → 42%; launch sell-through in VIP window ~60% of week-one inventory; complaint rate −35%.

Read the full stories: Sticky Digital case studies.

What to Do Next (Choose Builders, Not Broadcasters)

Plenty of agencies will send louder. Few will help you get closer. If you want a vendor, the world has options. If you want a partner who builds the system that keeps paying for itself—who raises second-purchase rates, shortens reorder intervals, protects inbox placement, and teaches your brand to win without bribery—start here:

• View all services (email, SMS, loyalty, subscriptions)
• Request a free audit (we’ll show you where the dollars hide without deeper discounts)
• 10 Traits of Top Retention Agencies (for RFPs with a backbone)