If you want more reviews in 2026, you don't "write better email copy" first.
You ship a deliverability-safe system and then tune timing + reminders until it prints.

Two truths:

The inbox is less forgiving than it was even 24 months ago. Google's enforcement ramped again starting November 2025.
"Bulk sender compliance" is no longer just a problem for giant brands. One high-volume campaign week can put you in "bulk sender" territory permanently for Gmail.

This chapter is the operator's playbook: get delivered, get opened, get the review—without setting your sender reputation on fire.

What changed (and why this matters more in 2026)

Inbox providers tightened the rules (and are actively enforcing them)

Google's requirements for senders include authentication, DNS hygiene, and keeping spam rates low (measured in Postmaster Tools). For bulk senders (≈5,000+ emails/day to Gmail), they explicitly require SPF + DKIM + DMARC, DMARC alignment, and one-click unsubscribe.

Gmail also states it's ramping enforcement starting November 2025, with temporary and permanent rejections for non-compliant traffic.

Microsoft followed suit for Outlook/Hotmail/Live: for domains sending over 5,000 emails/day, they announced requirements for SPF, DKIM, DMARC (at least p=none, aligned with SPF or DKIM) and indicated non-compliant mail will be filtered to Junk (and may later be rejected).

Implication: if your review request program is your review engine, deliverability is now part of your "review strategy," not a technical footnote.

The deliverability foundation (non-negotiables)

Think of this as "the lock on the front door." Without it, everything else underperforms.

A) Authentication + DNS checklist (minimum viable compliance)

For Gmail delivery, Google's sender guidelines call out:

SPF or DKIM for all senders; SPF + DKIM + DMARC for bulk senders
Valid forward + reverse DNS (PTR records)
Use TLS for transmitting email
Keep spam rates in Postmaster Tools below 0.3%

Operator note: this is not optional "best practice." These items are explicitly framed as requirements/guidelines tied to blocking/rate limiting.

B) One-click unsubscribe (yes, even for review requests)

For bulk senders, Google requires marketing/subscribed messages to support one-click unsubscribe, and shows the needed List-Unsubscribe headers (including RFC 8058 one-click behavior).

Practical takeaway: if a recipient can't easily leave, they'll hit "spam." Your spam complaint rate is now a hard constraint.

C) Bulk sender status sticks

Gmail defines bulk sender status as "close to 5,000 messages or more" in a 24-hour period and states that senders who meet that criteria at least once are permanently considered bulk senders.

Practical takeaway: plan your architecture (domains/streams) like you'll eventually be treated as bulk—because you probably will.

Timing: stop using "days after purchase" as your primary trigger

The only timing model that scales: delivery-based (or "ready to review")

Both Klaviyo and Okendo emphasize why fulfillment-based delays are unreliable: shipping delays cause customers to get asked before they've even used the product.

Practical timing framework:

Use a 2-layer model:
1. Trigger = Delivered (or "ready to review")
2. Delay = Category-based window, based on time-to-value

Suggested starting windows (then test):

Fast time-to-value (accessories, apparel basics, simple home goods): 3–7 days after delivery
Moderate time-to-value (footwear, cookware, gear): 7–14 days after delivery
Long time-to-value (skincare, supplements, complex products): 14–28+ days after delivery

Blunt truth: if you pick one universal delay, you'll systematically miss peak intent for at least one major segment.

Reminders: the sequence that wins (without killing your reputation)

The goal of reminders isn't "more emails"

It's one more chance at the right moment for people who didn't act the first time.

Recommended V1 sequence (simple, durable)

Email 1 — Review Ask (product experience)

Trigger: Delivered + delay window
Ask: star rating + 1 prompt (make it easy)

Email 2 — Reminder (frictionless)

Delay: +5 to +10 days after Email 1 (varies by category)
Ask: "Still willing to share quick feedback?"

Email 3 — Media / UGC follow-up (optional, segment-based)

Only to: customers with high CSAT signals, repeat buyers, or high-AOV products
Ask: photo/video + "how do you use it?"

Why this works in 2026: you get lift from reminders, but you reduce spam complaints by only emailing non-responders and by spacing appropriately.

Deliverability-safe content rules

You don't need "perfect copy." You need legitimate-looking email that doesn't trip filters or user suspicion.

A) Brand recognition beats cleverness

If the customer doesn't recognize the sender, they ignore or report.

B) Don't fight the unsubscribe link—use it

Yotpo explicitly warns against removing unsubscribe links and ties it to compliance + spam marking risk.

C) Avoid "spam-shaped" creative

Anything that looks like a sweepstakes blast, aggressive urgency, or "WIN $$$" vibes raises suspicion.

Operator rule: review request email ≠ promotion email. Keep it plain, specific, and obviously tied to a real order.

Monitoring: the few metrics that actually matter

A) Deliverability + compliance monitoring (minimum)

Gmail Postmaster Tools for spam rate + compliance status dashboard
Spam complaint rate target: < 0.3% for Gmail
Bounce rate, unsubscribe rate, and inbox placement (from ESP + seed tests)

B) Review-program performance monitoring (minimum)

Request → open → click → submit rate (by segment and by product category)
Review conversion rate by trigger type (delivered vs fulfilled)
Lift from Reminder #1 and Reminder #2
Complaint rate by message type (ask vs reminder vs UGC follow-up)

Hard rule: if spam complaints rise, you don't "send more." You tighten targeting and reduce volume until the system stabilizes.

Implementation checklist (V1, no overbuilding)

Week 1: Make delivery happen (literally)

Confirm SPF/DKIM/DMARC set up for the sending domain(s)
Confirm DMARC alignment + From domain alignment expectations
Confirm reverse DNS/PTR and TLS are in place
Confirm one-click unsubscribe headers + visible unsubscribe link

Week 2: Fix timing architecture

Switch trigger to delivered (or "ready to review") where possible
Define 2–3 product timing buckets (fast/moderate/long time-to-value)
Launch with conservative reminder spacing; only send to non-responders

Common mistakes (that quietly wreck your review volume)

Asking before delivery → low reviews + higher negative sentiment
One universal delay for every product → systematically misses peak intent
No unsubscribe (or hidden unsubscribe) → complaints → inboxing collapse
Ignoring spam rate → Gmail throttles/rejects; you blame "customers" instead
Sending reminders to everyone → you train the mailbox that your mail is unwanted

Benchmarks referenced

Up next (internal links)

Chapter 2: Trust, Authenticity, and Compliance
Chapter 3: UGC Photos + Videos: Benchmarks and Capture Systems

Review Requests That Still Deliver in 2026: Timing, Reminders, and Deliverability