Black Friday Email Marketing For Shopify: The Sends To Plan Now And The Flows To Freeze

Black Friday 2026 is Friday, November 27. The full BFCM calendar, its derivation, and the store side of the work all sit in the store-side Black Friday checklist: tracking, discount limits, code freezes, throttled checkouts. This post is the other half. It’s about what your email and SMS platform does when the volume actually arrives.

The failures below aren’t creative failures. They’re platform mechanics that behave one way on a normal Tuesday and a different way at peak, and almost all of them resolve as a skip rather than an error. Nothing turns red. The send just reaches fewer people than the report implies.

One note on sourcing. Every number here links to the page it came from, and every vendor recommendation is labeled as the vendor’s in the sentence where it appears, because a company that prices on send volume is not a neutral referee on how much you should send. We won’t re-caveat that in every paragraph.

Is any of this legal advice? No. Sections below quote the federal regulation and an industry rulebook directly so you can read your own configuration against the text, but BLKDG is a marketing agency and not your counsel. Compliance decisions belong with a lawyer who has seen your consent flows.

Klaviyo publishes a list of the reasons a flow message skips a profile, and it reads like a Black Friday failure inventory. Its troubleshooting documentation names Smart Sending, “Fails Flow Filters,” “Catalog Item Unavailable,” “Over Email Limit,” “Not Enough Sends Available,” “Unable to Create Coupon,” “No More Uploaded Coupons Remain,” “Error Retrieving External Data,” and “Missing SMS Consent.”

Every one of those is a person who was in your audience and didn’t get the message. None of them produce a bounce, a hard error, or an alert. They produce a smaller delivered count, which on Black Friday looks like normal variance in a number that’s moving anyway.

That’s the pattern for the whole weekend. The carrier stops accepting your texts at midday and returns a code you have to go looking for. The second and third emails of the day skip anyone who got the first. The coupon batch runs out and the extra recipients get nothing at all.

Do you need to register for A2P 10DLC to send Black Friday texts? Probably not, if you’re a US Shopify merchant on Klaviyo, and this is where the standard advice goes wrong. Klaviyo’s documentation on SMS sending numbers, updated March 9, 2026, states that “Toll-free numbers are the default sending numbers in Klaviyo for the US and Canada” and that “They are automatically created as soon as you set up SMS.”

Toll-free sits outside 10DLC’s throughput tiers and its campaign registration requirement. Twilio’s 10DLC throughput documentation states that “Toll-Free SMS is not affected by the throughput changes described in this article, nor is it subject to the new campaign registration requirements,” and that a US toll-free number “has a total of 3 MPS toward all US and Canada carriers by default.”

We’ve argued before that you don’t have an email problem you can fix with SMS, and the same discipline applies here: know what the channel is before you buy more of it. So the October task isn’t registration. It’s opening your platform’s SMS settings, reading which number type is actually sending, and confirming it’s verified. Klaviyo’s documentation says toll-free numbers “must be verified, although not all industries are eligible,” that verification “typically takes 2 to 5 business days,” and that it does “not recommend sending from unverified toll-free numbers.”

Klaviyo also documents that short codes take the longest of any number type to provision, and that except for short codes, verifying or registering typically takes no more than 7 to 10 business days. Short codes and vanity short codes are the only sending numbers Klaviyo says carry an additional monthly cost. If a short code is in your plan for this season, that decision needed to be made before now.

One documented gap to carry into your planning honestly: we could not find Klaviyo documentation stating whether its default US toll-free traffic is subject to a daily carrier segment cap, or what Klaviyo’s own aggregate throughput ceiling is. That’s an absence in the docs as of September 2026, not a statement that no cap exists. Klaviyo’s page does give a suitability threshold for toll-free, fewer than 300,000 messages at a time, but that’s guidance on picking a number type rather than a documented carrier cap. Ask your account team in October rather than discovering the answer on the day.

If you or your platform did put you on 10DLC, a second limit governs your day, and it’s a daily one rather than a per-second one. Twilio’s T-Mobile daily message limits documentation states that “You will receive a T-Mobile daily message cap based on your Trust Score (secondary vetting score),” that “This limit is applied at an EIN level, and shared among all A2P Brands and Campaign use cases registered under that EIN,” and that the limits “are shared if you are registered on multiple different messaging platforms or services.”

Read the sharing clause against your actual stack. Transactional shipping notifications from one vendor, a support texting tool, and your marketing platform can all be spending the same EIN-level allowance. Twilio documents the caps by Trust Score band.

Two special cases sit outside that table, both from the same Twilio page. Sole Proprietor brands have “a limit of 1,000 message segments per day.” Businesses in the Russell 3000 Index receive 200,000 segments and MMS per day by default, and T-Mobile “only removes the cap of 200,000 SMS segments + MMS per day if a business completes a process called Special Business Review.”

The score behind your band isn’t something you can improve in November. Twilio documents that a Trust Score is assigned during Standard Brand registration with The Campaign Registry, that secondary vetting assigns a score from 0 to 100, that “Trust Scores are static and do not automatically change over time,” and that “in general, smaller organizations and those with less business presence will receive lower scores.”

Here’s the arithmetic, and it’s ours off Twilio’s published numbers rather than a sourced claim. Twilio defines a segment as up to 160 GSM-7 characters and notes that more characters or a different character encoding can make one message into several segments. A merchant in the 25-49 band has 10,000 segments a day toward T-Mobile. Two one-segment sends on Black Friday to 5,000 T-Mobile subscribers consumes the entire day’s allowance.

We don’t know your T-Mobile share, and you shouldn’t assume one. Pull the actual count and multiply it by your planned sends per day, then add whatever your encoding and MMS use do to the segment count, and remember every other brand under the same EIN is drawing on the same allowance. When it’s gone, Twilio documents that messages come back undelivered with error 30023, and that “The daily limit resets every day at midnight, Pacific US Time.”

Buying more numbers doesn’t buy your way out. Twilio states that a campaign’s throughput “is shared across all US/Canada long code numbers allocated to your campaign, and all wireless carriers,” and that splitting messages across a collection of local numbers gets you the same limit. The industry rulebook the carriers enforce has a name for the attempt: the CTIA Messaging Principles and Best Practices, dated May 2023, tells senders they “should not engage in Snowshoe Messaging.”

If registration is in front of you, plan against a range rather than a number. On September 8, 2026, Twilio’s throughput page carried a banner saying campaign reviews were running 5 to 10 days, while its T-Mobile daily limits page said 10 to 15.

Those are two live pages on the same vendor’s help center, read the same day, disagreeing by a factor of two on the upper bound. We’re not going to average them into a fake number. Both describe review times as elevated, and a merchant who starts registration in November is betting on the shorter one.

How many emails should you send on Black Friday? Klaviyo’s own BFCM daily sending guide publishes a day-by-day answer, and it’s a vendor recommendation from a company that prices on volume. We reproduced its cadence table in the store-side checklist rather than here, because the number of sends isn’t the interesting part. The condition attached to it is.

Klaviyo’s guide states that “With the right segmentation strategy, you could send 4 separate email campaigns that reach 4 distinct customer segments in 1 day without damaging your sender reputation.” The operative words are “4 distinct customer segments.” That cadence is a segmentation prescription wearing a volume prescription’s clothes.

Now put it next to Klaviyo’s Smart Sending documentation, which sets an email default window of 16 hours and an SMS default window of 24 hours. Three emails in one day against a 16-hour window, or two texts in one day against a 24-hour window, only work if the audiences don’t overlap. Copy the cadence table without building the segments underneath it and the platform resolves the conflict for you.

It resolves it by skipping, and the skip is permanent. Klaviyo documents that “Messages skipped due to Smart Sending are not rescheduled automatically,” and that “Currently, it’s not possible to resend a text message or push notification to someone who was skipped due to Smart Sending except by doing so manually.” Send two and send three don’t arrive late. They don’t arrive.

Turning Smart Sending off is the other resolution, and it removes your only automatic guardrail against over-messaging on the four days you’re most likely to over-message. Changing the window on the morning of the sale doesn’t help either. Klaviyo states that updating the window “does not retroactively affect recipients” and that “The amount of the time is the same as the Smart Sending window at the time you send,” so the profiles already sitting under a longer timer stay there.

Most black friday marketing ideas resolve into three configuration items: a segment, a send window, and a coupon count. Klaviyo’s guide gives you a starting point on the first one, recommending that you exclude people who purchased within the last day from Black Friday sale campaigns and within the last 4 days from Cyber Monday campaigns. Those exclusions are the difference between a cadence and a collision.

One more Smart Sending behavior matters later in this post. Klaviyo states that “Smart Sending only applies to marketing messages. Transactional messages are never skipped.”

Most merchants believe their platform enforces quiet hours across everything they send. Klaviyo’s documentation on changing quiet hour settings says otherwise, in one sentence: “Quiet hours are only available for flows; however, you will get a warning if you attempt to send a campaign during quiet hours.”

Can you schedule a midnight Cyber Monday blast? The platform will let you. A campaign scheduled into a restricted window shows a warning and sends, which means the protection you’re relying on covers your abandoned-cart flow and not the doorbuster announcement you spent three weeks building. The sends you’re worried about are the unprotected ones.

For the clock itself, go to the regulation rather than to a vendor. The FCC rules implementing the TCPA, at 47 CFR 64.1200, state that no person or entity shall initiate any telephone solicitation to “Any residential telephone subscriber before the hour of 8 a.m. or after 9 p.m. (local time at the called party’s location).” That eCFR page reports itself as current through September 3, 2026.

We’re pointing at the regulation on purpose. Two live Klaviyo help pages carried two different quiet-hours windows on September 8, 2026, which is a good reason to take your clock from the primary text and treat your platform’s default as a configuration setting rather than as a statement of law.

The federal rule attaches that window to a defined term, and the definition has carve-outs. Section 64.1200(f)(15) defines “telephone solicitation” as a call or message encouraging a purchase, but says the term “does not include a call or message: To any person with that person’s prior express invitation or permission; To any person with whom the caller has an established business relationship; or By or on behalf of a tax-exempt nonprofit organization.”

Whether those carve-outs reliably place marketing texts to opted-in subscribers outside the window in current practice is contested litigation, not settled documentation, and we’re not going to assert it in either direction. State mini-TCPAs are separate statutes and several are stricter; Klaviyo’s documentation names specific states with tighter windows, and we didn’t pull those statutes, so don’t take a state’s hours from a help article. The operational answer is to configure quiet hours in October and not reason your way out of them at 11pm on Black Friday.

Two ordering details from Klaviyo’s quiet hours documentation affect how your weekend actually behaves. Both quiet hours and Smart Sending are “checked at send time, not the time you scheduled the message,” and “quiet hours are checked before Smart Sending.” Klaviyo also states that “By default, messages marked as transactional do not have quiet hours enabled,” which is the first half of a problem the flows section finishes.

Two BFCM mechanics run straight into the regulation, and both are configuration you can check this month.

The first is gating. Section 64.1200(f)(9) requires that prior express written consent include a clear and conspicuous disclosure that “The person is not required to sign the agreement (directly or indirectly), or agree to enter into such an agreement as a condition of purchasing any property, goods, or services.” A Black Friday mechanic that hands over the discount only after the shopper opts in, or a checkout that makes the SMS box feel mandatory, is the thing that sentence is about.

The second is your opt-out confirmation. Section 64.1200(a)(12) exempts a one-time confirmation text “as long as the confirmation text merely confirms the text recipient’s revocation request and does not include any marketing or promotional information.” A save-the-subscriber message offering one last code, sent after someone texts STOP, is not that message. Open your platform’s opt-out reply and read it against that clause before the weekend.

The revocation rules themselves are broader than most SMS programs assume. The regulation says a called party may revoke “by using any reasonable method,” lists “stop,” “quit,” “end,” “revoke,” “opt out,” “cancel,” and “unsubscribe” as per se reasonable, and then requires that a reply using other words be treated as valid “if a reasonable person would understand those words to have conveyed a request to revoke consent.” It also states that senders “may not designate an exclusive means to request revocation of consent,” and that requests must be honored “within a reasonable time not to exceed ten business days.”

Above the law sits the carriers’ own rulebook, which they enforce by filtering. CTIA’s May 2023 Messaging Principles tell senders to document opt-in consent by retaining the timestamp of consent acquisition, the acquisition medium, a capture of the experience used to secure consent, the specific campaign the opt-in was provided for, and the IP address used to grant it. That’s an audit trail you assemble before a complaint, and CTIA also states that “A Consumer opt-in to receive messages should not be transferable or assignable,” which is the answer to any list you were offered for the season.

Should you pause your flows during the sale? Mostly no, and pausing is a blunter instrument than merchants expect. Klaviyo’s flows documentation states that “If you change a message in a live flow to draft, it will be skipped in the sequence,” so the people in that flow don’t get the message later. They don’t get it at all.

Your flows are the part of the program that pays rent the other eleven months of the year, which we’ve written about in the lifecycle that pays rent. The instrument you actually want is a profile filter, and the reason is in the same documentation. Klaviyo states that “Before each component (email, SMS, split, etc.), profile filters will be re-checked to ensure that recipients still meet the criteria of the flow,” and separately that “trigger filters are not checked again at send time.” A trigger filter added on Black Friday morning does nothing for anyone already moving through the flow. A profile filter added in the week of November 9 gates every message that hasn’t sent yet.

Time delays behave the same way. Updating a delay “will not impact any already scheduled messages,” and only affects messages scheduled after the change. Every flow decision below is a week-of-November-9 decision, not a Friday-morning one.

Klaviyo’s price drop flow documentation, updated February 13, 2026, describes a flow that lets you “Choose when a price drop flow will trigger; i.e., at what amount or percentage a product’s price needs to drop.” On a normal Tuesday that fires for a handful of products and a handful of people.

A sitewide markdown is that same event, on every product, for every subscriber who browsed any of them, at the hour your planned campaign is going out. Two sends now compete for the same inbox and the same Smart Sending window, and only one of them was on the calendar.

Raising the threshold on the day doesn’t undo it. Klaviyo states that “You can adjust the trigger at any point, but it will only apply to events triggered after you change it.” The events that already fired are already in the flow.

One thing we could not verify, and it changes the advice, so we’re not going to paper over it. Klaviyo’s documentation says the trigger watches “a product’s price” and doesn’t state whether that value is the catalog price or a price after discounts. So we don’t know whether a Shopify automatic discount, which leaves catalog prices untouched, fires this flow.

If your sale changes catalog or compare-at prices, assume it fires and freeze the flow. If your sale runs entirely on automatic discounts, test it in the week of October 26 rather than assuming either way.

Two of the flow’s documented conditions cut in your favor during a sale. Klaviyo states that price drop flows “will only trigger for items that are listed as in stock,” that they “will not send to anyone who has already purchased the item,” and that these conditions “are checked both at the trigger and before any messages send out.”

Klaviyo’s back in stock documentation, updated February 24, 2026, states the limitation plainly: “Note that it’s not possible to check if the item is still in stock before sending a second message. After the initial message is sent, Klaviyo cannot check the inventory for the item to see if the item has gone out of stock again.”

On a normal restock that’s fine, because the restock lasts days. On Black Friday a restock can last minutes. Message one goes out, the item sells out, and message two sends to everyone who didn’t act on message one, pointing at a product they can’t buy.

That’s a documented platform limitation rather than a misconfiguration, so the fix is structural. Cut the sequence to a single message for the sale weekend, or freeze it and reach that audience with a campaign instead, which is what Klaviyo recommends for anyone in a back in stock report.

The abandoned cart flow carries the highest purchase intent in the building during a sale, and pausing it to avoid discount stacking trades a lot of revenue for a problem you can solve with a filter. Strip or gate the incentive, add the profile filter, and leave it running.

Winback is the opposite call. Klaviyo’s winback documentation describes a flow whose mechanic is an incentive plus urgency, with a second email that reinforces “the incentive from the first email as well as a sense of urgency (e.g., by setting an expiration date on the discount).” During a sitewide sale that incentive is either worse than the public offer or stacks on top of it, and the stacking math is in the store-side checklist rather than here. Remove the discount and keep the message.

Post-purchase flows are the ones that ignore every guardrail you set for the weekend, and it’s a consequence of two documented defaults rather than a bug. Smart Sending never skips transactional messages, and quiet hours are off by default for messages marked transactional. So a post-purchase sequence marked transactional sends on top of every campaign, at any hour, to people who just bought.

Whether post-purchase upsell content conflicts with concurrent sale pricing isn’t documented by Klaviyo anywhere we could find, so treat what follows as our operating advice rather than platform behavior: open every post-purchase message, look for a price, an offer, or a “come back soon” incentive that the sale has already beaten, and rewrite or gate it before November 9.

Your black friday email templates can be pixel-perfect and still not send. Klaviyo’s skip documentation lists “Catalog Item Unavailable,” which skips a profile “because a product in the rendered email content is currently out of stock or not available.” Any template with a dynamic product block is exposed to that, and doorbusters are the products most likely to sell out.

Think about what that does to an abandoned-cart email on Friday afternoon. The cart contains the item that just sold out, so the rendered content contains an unavailable product, so the message is skipped. The highest-intent person in your database gets nothing, and your skip count for that flow was already supposed to be large.

That last part is why the skip report doesn’t warn you. Klaviyo documents that “abandoned cart flows should always have a lot of skips, as everyone who begins to check out enters the flow, but those who then place an order are skipped.” A new failure mode hides inside an expected number.

Two more skip reasons come from your plan rather than your catalog: “Over Email Limit,” which fires when you exceed your account’s email sending limit, and “Not Enough Sends Available,” which is the same failure on the SMS side. Campaigns consume that allowance first because you scheduled them first, and flows are what run out of room. Check your plan allowance against your planned November volume in the week of November 2, while changing it is still a conversation instead of an emergency.

Klaviyo also lists “Error Retrieving External Data,” naming Shopify explicitly as an example of the external source, and “Missing SMS Consent,” which skips anyone without a consent timestamp. The second one is a good argument for auditing consent records in October rather than counting phone numbers.

Klaviyo’s documentation on unique coupon codes for Shopify, updated March 30, 2026, contains the single most expensive sentence in a BFCM setup: “If your scheduled campaign is set to ‘Determine recipients at send time,’ and the actual number of recipients is greater than the number of codes you generate at send time, the extra recipients will be skipped and will not receive the email.”

Now apply your own November. Your list grows through the month, you generated codes against the count you had when you built the campaign, and the difference between those two numbers is people who get nothing. Klaviyo’s documented fix is to “Create a separate coupon for each campaign,” which makes the required count explicit per send, and that’s an October task rather than a Black Friday one.

The replenishment behavior has the same shape. Klaviyo states that codes for live flow emails “automatically replenish daily; however, if you use all codes before the replenishment, the next attempt to assign a coupon will be skipped due to insufficient codes available.” A flow that burns its daily pool by noon spends the rest of the day skipping.

The skip reason “Unable to Create Coupon” names the peak-load version of this directly, citing “sending too many coupons out in a short amount of time” and recommending “adding coupon codes in advance to a campaign.” Klaviyo also notes the initial coupon can take about 3 minutes to generate, and that Shopify enforces a limit of 20 million unique discount codes per store, at which point you have to delete codes in the Shopify admin before generation resumes.

Then there’s the behavior that makes freezing your promo config a mechanical requirement rather than a preference. Klaviyo documents that “If you change the coupon definition in Shopify, then coupon codes that have already been sent will be impacted,” and gives the example of a code sent with a $20 minimum purchase that a merchant later raises to $40 in Shopify: “the previously sent coupon codes will be updated to the new definition ($40 minimum purchase).”

Read that as an operator. Raise a minimum spend on Saturday afternoon to protect margin, and the codes sitting in Friday’s inboxes now carry Saturday’s rule. The customer holding an email that promised one thing hits a checkout that enforces another, and nothing in your ESP reflects the change. Freeze the Shopify price rules behind every emailed code when you freeze the flows.

Shopify’s discount methods documentation describes two mechanisms with a trade-off that lands squarely on email. Shopify’s page isn’t quotable here, so what follows is our paraphrase of it rather than Shopify’s wording.

Shopify describes discount codes as codes a customer enters at checkout, commonly used for marketing strategies like email campaigns, and notes they can create engagement and urgency while also being forgotten at checkout. It describes automatic discounts as discounts applied in the cart and at checkout when conditions are met, commonly used for sitewide sales and collection promotions, and notes customers might not realize they’re getting one.

The email consequences follow from that. A code is attributable to the send that carried it, and it’s also the thing that gets forgotten at checkout, consumes one of Shopify’s per-order code slots, has to be generated per recipient, and freezes your Shopify price rule for the duration. An automatic discount can’t be forgotten and can’t be attributed to the email that drove the visit.

Our read: run the sitewide sale as an automatic discount and reserve codes for segment-specific offers where attribution actually changes a decision. Running a sitewide sale as an emailed unique code is how merchants arrive at the coupon-exhaustion failure above, with the extra recipients silently skipped.

Klaviyo has every incentive to say otherwise, and its own BFCM guide states that “not every brand needs to offer massive discounts” and that “higher discounts do not necessarily equate to higher conversions.”

Google’s email sender guidelines tell senders to “Send email at a consistent rate. Avoid sending email in bursts,” to “Start with a low sending volume to engaged users, and slowly increase the volume over time,” and to “Avoid introducing sudden volume spikes if you do not have a history of sending large volumes.” It adds that “immediately doubling previously sent volumes suddenly could result in rate limiting or reputation drops.”

Keep Google’s conditional. It says could, not will, and we’re not going to upgrade it. What the text does establish is that a Black Friday campaign is a sudden volume spike into a list that includes people who haven’t opened anything since last November, and the only place to build sending history is the eight weeks before it.

Google also documents what monitoring looks like while you ramp: “regularly monitor server responses, spam rate, and the sending domain’s reputation,” and reduce volume if “messages start bouncing or start being deferred,” then increase slowly again. When you exceed quota, “Gmail typically rejects messages with SMTP error code 4.7.28,” you should “Do not send email for at least 10 minutes,” and if the error doesn’t name which quota, “assume that all three are affected.” Note that “The IP address quota is shared for all senders that use that IP address,” which is your shared-ESP-infrastructure risk in one sentence.

Every send-volume benchmark for this weekend comes from a company that sells sending, and we’d rather say that than pretend a neutral number exists. Klaviyo’s own report on BFCM 2025, published on its blog December 2, 2025, puts SMS send volume across its customers up 34% year over year, under a heading about text messaging specifically. It publishes no equivalent all-channel or email-only send-volume growth figure, so there’s no sourced number here for what happened to email volume, and we’re not going to borrow the SMS one to stand in for it.

SMS has its own version of the ramp, and Klaviyo’s SMS deliverability documentation states the vendor’s recommended floor: send at least 2 to 6 SMS messages per month, using engagement segments so you text the full list regularly, and text unengaged subscribers “at least once a month.” A list that’s been silent since last Black Friday is below that floor by the vendor’s own standard, and the engagement signals carriers evaluate are stale.

The instinct to protect the main domain by sending the promotional blast from a new subdomain runs into a definition. Google’s sender guidelines FAQ states that “A new domain is defined as any domain that hasn’t sent more than 5,000 emails a day to personal Gmail accounts since January 1, 2024,” and that “While all bulk sending domains must comply with the requirements, the enforcement progression for new domains will be on an accelerated timetable.”

A subdomain created in October is a new domain under that definition. Google doesn’t publish what “accelerated” means numerically, so you’re volunteering for a stricter enforcement path whose parameters aren’t documented, in exchange for protecting a reputation you could have warmed instead.

Set up measurement in the same pass. Google’s Postmaster Tools setup documentation states that you add “either the DKIM (d=) domain or the SPF (Return-Path) domain,” that subdomains have to be added separately to see them independently, and that Postmaster Tools “won’t display information about your email until your domain is verified.” Verification typically happens right away and can take up to 10 minutes.

We found no documentation of a backfill for newly verified domains, so treat your data as starting the day you verify. Verifying on Black Friday morning gives you a number with nothing to compare it against. Verify in September.

Yahoo measures your complaint rate against a base most merchants don’t use. Its sender best practices state that “Spam rate is calculated in our system based on mail delivered to the inbox,” with an explicit instruction to keep that in mind “when referencing CFL data and calculating the rate in your own system.”

A spreadsheet dividing complaints by messages sent produces a smaller number than the one Yahoo is judging, because Yahoo’s denominator excludes everything that never reached an inbox. The instrument Yahoo names is the Complaint Feedback Loop, and it states that “An active CFL is needed for all DKIM domains to make sure you’re processing complaints quickly.” Sign your mail with DKIM and enroll the domain before the season, not during it.

Yahoo also tells senders to “Segregate Email types by IP or DKIM domain,” noting that “Each IP and DKIM domain has a reputation, which can impact the delivery of your email.” That’s the sourced answer to whether your Black Friday promotional blast should share a stream with your order confirmations. It shouldn’t, and separating them is a November-safe change only if you make it early enough to have sending history on both.

These weeks line up with the twelve-week grid in the store-side checklist, so the two plans run side by side. Each Monday date is a real date on the 2026 calendar, and Black Friday is Friday, November 27.

Klaviyo’s SMS deliverability documentation names the exact weekend you’re planning for: “for a small percentage of messages, carriers can be extremely delayed in issuing DLRs or never provide them at all (even in cases when the recipient did, in fact, receive your message). This is more common with small regional carriers, when sending MMS, or during peak sending hours (e.g., during Black Friday/Cyber Monday).”

That produces a specific 10am problem. Klaviyo marks a message “Delivered” only “when carriers explicitly confirmed that an SMS was delivered,” and “Sent” if carriers “did not confirm the delivery or issue a failure.” A wall of Sent tells you nothing about whether the message landed, and the instinct is to send it again.

Resending into an unconfirmed send doubles your segment consumption against a daily cap you can’t see in real time. That’s the decision to make in October and write down, because at 10am on November 27 the person making it will be reading an ambiguous dashboard under time pressure.

Learn the failure vocabulary before you need it. Klaviyo defines “Carrier Violation” as the carrier filtering the message out, “Message Blocked” as a block by a carrier, Klaviyo, or the recipient, “Device Unreachable” as the device being off or out of service area, “Device Incapable of Receiving SMS” as a landline or non-SMS number that Klaviyo automatically unsubscribes, and “Unknown” as the carrier not reporting a reason.

One more reason the freeze includes your landing pages: Klaviyo documents that carriers check “the message, URL, or linked landing page” for filtered terms, that each carrier applies its own criteria, and that carriers “sometimes don’t confirm delivery or failure at all to prevent people from learning more about their checks.” A holiday collection added to a linked page after your texts were approved is a content change to an asset the carrier reads.

Not on subject lines. Not on templates. On six configuration decisions made while there’s still time to test them.

Which number is sending. Whether your segments are disjoint. Where quiet hours are actually enforced.

Which flows can behave during a markdown. How many coupon codes exist. What you’ll do when the delivery report goes quiet.

Every one of those is invisible until peak volume makes it visible, and by then the answer is whatever you configured in October. That’s the whole argument, and it’s why the retention plan gets built now rather than during the week of November 23.

If you want an outside read on your flows, your segments, and your sending setup before the season, that’s what our free Growth Audit is. Not a sales call. Not a quote request. A clear look at what’s going to skip, why, and what to change while changing it is still cheap.

If you already know the work is bigger than an audit, start with our Klaviyo email and SMS work. You built something worth finding. Make sure it gets delivered.