Klaviyo Deliverability: Sending Domains, DMARC and Engaged Sending

What affects deliverability in Klaviyo?

Klaviyo deliverability depends on whether mailbox providers trust your domain, and that comes down to two things you control: proving the mail is really from you, and sending only to people who want it. Authentication is the first part. Engaged segments, list hygiene and a sunset flow are the second.

Klaviyo provides the sending infrastructure, but Gmail, Yahoo, Microsoft and the rest decide where your email lands, largely based on how their users react to it. No setting guarantees inbox placement.

This guide covers the Klaviyo-specific side. For the underlying standards, see our guides to SPF, DKIM and DMARC.

Set up a branded sending domain

A branded sending domain lets Klaviyo send your email from a subdomain of your own website domain, rather than from Klaviyo’s shared domain. Klaviyo previously called it a dedicated sending domain, and you’ll still see both names. Without one, recipients may see “via klaviyomail.com” next to your sender name, and your reputation is tangled up with Klaviyo’s shared infrastructure.

With one, mail is signed with your own domain, so DMARC can pass in alignment and the reputation you build belongs to you.

Choosing the subdomain

The sending domain is a subdomain of your root domain, such as send.yourbrand.com. Klaviyo notes “send” is the most common choice. It must be a subdomain you don’t already use for anything else.

Klaviyo now supports separate sending domains per send type, each with its own reputation: marketing, transactional and service (for its helpdesk features), suggested as “send”, “updates” and “support” on the same root domain. A separate transactional domain means a marketing reputation problem won’t drag order confirmations into spam with it.

Keep your From address on the root domain (hello@yourbrand.com), not on the sending subdomain. Replies to an address on the sending subdomain won’t reach you.

DNS records

Klaviyo offers two setups:

• Dynamic routing, which Klaviyo recommends. You add four NS records that delegate the sending subdomain to Klaviyo, plus a TXT verification record on your root domain. Klaviyo then manages the subdomain’s SPF and DKIM itself.
• Static routing, using CNAME records you manage, including two DKIM CNAMEs. The selector names depend on send type (km1/km2 for marketing, kt1/kt2 for transactional). Older setups using kl1/kl2 keep working.

Klaviyo can publish the records through Entri for supported DNS providers. Propagation can take up to 48 hours.

Do you need to warm up a new sending domain?

Yes, if the account is new or the domain was registered in the last 30 days. Klaviyo says it’s essential to warm marketing infrastructure over the first two to four weeks. In practice, that means starting with your most engaged recipients and widening the audience gradually, rather than switching on a full-list campaign on day one.

Existing senders adding their first branded marketing domain don’t need to re-warm if the domain is at least 30 days old and has sent email before. Transactional and service domains usually don’t need warming because their volume is low. Our domain warmup guide covers the process in more detail.

DMARC: the minimum and the next step

DMARC tells mailbox providers what to do when mail claiming to be from your domain fails authentication, and where to send reports about it. The major providers now require bulk senders to publish one.

During sending domain setup, Klaviyo can generate a DMARC record for you: v=DMARC1; p=none;. That meets the bulk-sender requirement. It doesn’t ask providers to quarantine or reject anything; it’s a monitoring policy.

Two things to do beyond the minimum:

1. Add reporting. A rua tag sends aggregate reports to an address or a DMARC reporting service. Yahoo strongly recommends it. Without reports, you can’t see which other services send as your domain, such as your helpdesk, invoicing tool or Google Workspace.
2. Move toward enforcement when the reports are clean. Once every legitimate sender passes, you can step to p=quarantine and eventually p=reject. Do this slowly. Tightening the policy before you’ve found every sender is how businesses discover their invoices have been landing in spam for a month.

Alignment matters as much as the record. DMARC passes only when SPF or DKIM passes for the same domain shown in the From address (or a subdomain of it, under the default relaxed alignment). A branded sending domain on your own root domain gives you that alignment. Sending from Klaviyo’s shared domain while your From address says yourbrand.com doesn’t.

Gmail, Yahoo and Microsoft sender requirements

All three large consumer mailbox providers now publish requirements for high-volume senders. They overlap heavily.

Gmail treats anyone sending 5,000 or more messages a day to personal Gmail accounts as a bulk sender, and Klaviyo points out the count includes transactional mail. Once you’re classified as a bulk sender, it’s permanent. Bulk senders need SPF and DKIM, a DMARC policy of at least p=none that passes with alignment, one-click unsubscribe on marketing messages (the List-Unsubscribe header standard in RFC 8058), and unsubscribes honored within two days. Google asks senders to keep the user-reported spam rate below 0.1% and never let it reach 0.3%. Google stepped up enforcement from November 2025, meaning non-compliant mail can now be temporarily delayed or permanently rejected, not just filtered.

Yahoo asks all bulk senders for SPF and DKIM, a passing DMARC policy of at least p=none with alignment, a working one-click List-Unsubscribe header plus a visible unsubscribe link in the body, unsubscribes honored within two days, and a spam rate below 0.3%.

Microsoft (Outlook.com, Hotmail and Live addresses) introduced requirements for domains sending more than 5,000 messages a day, effective May 2025: SPF, DKIM and DMARC at p=none or stronger. Non-compliant mail is junked first, with rejection as the stated next stage.

What this means in Klaviyo terms:

• Authentication is handled by your branded sending domain and DMARC record, as above.
• The unsubscribe mechanics are mostly Klaviyo’s job, but you still need a visible unsubscribe link in every marketing template. Don’t hide it in tiny gray text.
• The spam rate is entirely yours. It’s driven by who you send to and how often, which is the rest of this guide.

Set up Google Postmaster Tools on your root domain if you haven’t. It shows the spam rate Google measures and, in its current version, a compliance status view against these requirements. Klaviyo can’t show you Gmail’s own numbers. Our sender reputation guide explains how to read it.

Read Klaviyo’s Deliverability hub

Klaviyo’s account-level view lives under Analytics > Deliverability (Channel health in some accounts). On the Email tab:

• Score: a 0 to 100 deliverability score updated daily, based on the last 30 days of open, click, bounce, unsubscribe and spam complaint rates. It needs at least 1,000 emails sent in the last 30 days. Bands run from Poor (below 50) to Excellent (90 and above). The Factors view compares each metric with Klaviyo’s benchmarks.
• Reports: key metrics broken down by inbox provider or email domain. This is where you spot a Gmail-only or Microsoft-only problem, which an account average hides.
• Bounce details: bounces grouped into categories by provider, useful for telling a list problem from a blocking problem.

The score is an early warning, not a measure of inbox placement.

Bounces and suppression in Klaviyo

Klaviyo suppresses addresses automatically in the obvious cases. A hard bounce (an address that doesn’t exist) is suppressed immediately. Soft bounces (full mailbox, temporary server problem) are suppressed after seven in a row, counting only the past two years, and any successful delivery resets the count.

Seven consecutive soft bounces can take months for a weekly sender, so Klaviyo suggests a chronic soft bounce segment if you want to act sooner.

Suppression is account-wide for email marketing. It doesn’t affect SMS or push.

Send campaigns to engaged segments

The single biggest lever most Klaviyo accounts have is who receives campaigns. Sending every campaign to the entire subscriber list, including people who haven’t clicked in a year, pushes up complaints and drags down engagement signals. Providers notice.

An engaged segment is a dynamic segment of people who have shown recent interest. Typical conditions combine:

• can receive email marketing,
• and any of: clicked an email, was active on site, placed an order, or joined the list, within a recent window.

The window depends on how often you send and how often customers buy. A brand sending daily might use 30 or 60 days; one sending twice a month might use 90 or 180. Many accounts use tiers, sending most campaigns to the tightest segment and widening only for major moments.

Be careful leaning on opens. Apple Mail Privacy Protection records opens for many messages nobody read, so an “opened in the last 90 days” condition includes a lot of people who aren’t actually engaged. Exclude Apple privacy opens if you use opens at all, and give more weight to clicks, site activity and orders. Our Klaviyo segmentation guide goes into building and maintaining these segments.

A short scenario: a brand’s engaged segment was built three years ago on “opened in the last 180 days”. Since then, Apple’s privacy changes have quietly inflated it, and it now includes most of the list. Campaigns still say “engaged segment” in the audience field, but in practice they go to almost everyone, and the brand can’t work out why Gmail placement keeps sliding.

Frequency and Smart Sending

Smart Sending skips messages to anyone emailed recently (16 hours by default). It stops flows and campaigns stacking on one person, but it isn’t a frequency strategy. It won’t fix complaints driven by sheer volume.

Build a sunset flow

A sunset flow is the last chance for long-inactive subscribers before you stop emailing them. It sends a short series asking whether they still want your email, and tags anyone who doesn’t respond so you can suppress them. It’s the counterpart to the win-back flow: win-back is for customers who stopped buying, sunset is for subscribers who stopped engaging. The win-back flow guide covers the other side.

Klaviyo’s suggested setup:

1. Use the Sunset (Email) segment from the segment library under Audience > Lists & segments. It targets profiles that can receive email marketing, were created at least 180 days ago, have received at least five emails in the last 72 weeks, and have never opened, clicked, visited the site, viewed a product, started checkout or ordered. Adjust it to your own sending pattern.
2. Trigger the flow on Added to segment for that segment.
3. Add profile filters for Opened Email zero times since starting this flow and Clicked Email zero times since starting this flow, so anyone who responds drops out.
4. Send one to three emails. Klaviyo advises no more than three. Say plainly that you’ll stop emailing unless they want to stay, and give them an easy way to say so.
5. Wait a grace period after the last email (Klaviyo’s example is three days for daily senders, seven to ten for less frequent ones).
6. Add a property update that sets a Boolean property, such as Unengaged, to true.

The property only marks profiles. It doesn’t suppress them, and there’s no native flow action for email suppression. To finish the job, build a segment where that property is true and use Suppress current members from the segment’s menu. That suppresses only the profiles in it at that moment, so repeat it on a schedule. Put a reminder in someone’s calendar, or the tagged profiles quietly pile up.

Profiles already in the segment don’t enter a new flow automatically. Use “Add past profiles” on the trigger to run the backlog through, and expect a large first batch.

Keep the list clean at the source

Sunset flows clean up after the fact. Most problems start with how addresses arrive: old imports without clear consent, checkout customers who never opted in (they arrive as Never subscribed), and bot or typo signups from unprotected popups. Double opt-in on higher-risk sources helps, at the cost of some real signups who never confirm. Our email list hygiene guide covers sources, validation and re-permission.

Common Klaviyo deliverability mistakes

• Sending from Klaviyo’s shared domain years after outgrowing it.
• A DMARC record at p=none with no reporting, left untouched since 2024.
• One “engaged” segment based on opens, now inflated by privacy features.
• A sunset flow that tags profiles that are never actually suppressed.
• Judging deliverability only from Klaviyo’s account averages, never by inbox provider.

If you’ve worked through these and placement is still slipping, the cause is usually sender reputation that needs a structured recovery plan. That’s what our deliverability improvement work covers.