Why Are My Klaviyo Emails Going to Spam? A Diagnostic Walkthrough

If you are reading this, something shifted. Either your open rates dropped, a specific customer reported seeing your email in spam, or your internal tests started landing in Gmail's spam folder when they used to land in the inbox. The good news is that almost every cause is diagnosable and most are fixable. The less good news is that the symptom "going to spam" can come from seven distinct root causes, and the fix for one will not address the others.

This walkthrough covers the seven most common reasons Klaviyo emails end up in spam, ranked by how often we see each in practice. Work through them in order. The first one you find that matches your symptoms is almost certainly the one to fix, and you will waste less time than trying to address everything at once.

1. Authentication Is Broken or Misaligned

This is by far the most common cause, and also the most underdiagnosed, because Klaviyo's dashboard shows "authentication" as a green checkmark when only SPF is passing, regardless of what DKIM and DMARC are doing.

Check three things at every sending domain you use in Klaviyo:

• SPF passes for the sending source. Klaviyo's SPF include should be in your DNS for any domain you send from.
• DKIM signs and passes alignment. Every Klaviyo sending domain should have CNAME records pointing to Klaviyo's DKIM keys. The CNAMEs must be active in DNS, and when you send a test message and check the headers, the DKIM signature must match the From domain.
• DMARC is published, and the From domain aligns with either the DKIM d= or the SPF return-path. If DMARC is published with p=reject or p=quarantine, and alignment fails, your mail gets filtered or rejected at the receiving end regardless of anything else.

How to test it quickly: send a message from your Klaviyo account to a Gmail address you control. Open the message, click the three-dot menu, select "Show original." The result shows SPF, DKIM, and DMARC statuses explicitly. Any of them showing "fail" or a DMARC column missing entirely is a strong signal.

What tends to break in Klaviyo specifically: DKIM CNAMEs that were added when the account was set up, then became stale after a DNS migration or a domain ownership change. CNAMEs that point to the wrong Klaviyo key. Subdomain sends that are not authenticated because the DKIM records only exist for the root domain.

Fix: correct the DNS records, wait for propagation (usually under an hour for CNAME, up to 24 hours worst case), re-verify authentication in Klaviyo, send a test, confirm the headers look right.

2. Your List Is Carrying Dead Weight

The second most common cause is list hygiene. Mailbox providers use engagement as a reputation signal. Sending to addresses that do not open, click, or interact for extended periods damages your reputation at the ISP level, which then increases the probability that your mail goes to spam even for your engaged subscribers.

The specific mechanics:

• Gmail tracks engagement per sender per recipient. If a large share of your Gmail recipients never open, Gmail gradually filters more of your mail to spam, including messages to recipients who would have opened.
• Microsoft uses aggregate engagement as a deliverability input. Low engagement rates at Microsoft domains (Outlook.com, Hotmail, Live) correlate strongly with increased filtering.
• Yahoo and AOL apply similar patterns, with higher sensitivity to complaint rates.
• Spam traps are the worst case. A spam trap is an email address that exists only to catch senders with poor list hygiene. Sending to a spam trap, even once, is a direct reputation hit. Recycled traps (addresses that were once real but have been abandoned and reactivated as traps) are the most common, and they enter lists through old subscribers who stopped engaging.

What tends to break in Klaviyo specifically: sunset flows that are configured to trigger on "no opens in 90 days" will not catch subscribers whose opens are inflated by Apple Mail Privacy Protection. Those subscribers look engaged while being completely inactive. Re-engagement campaigns that target long-dormant subscribers send into an audience that mailbox providers already consider cold, and the reputation damage can outweigh any recovered revenue.

Fix: build a sunset policy on clicks, conversions, and site visits rather than opens. Suppress subscribers who have not engaged meaningfully in 90 to 180 days depending on your purchase cycle. Do this before running a re-engagement flow, not after.

3. Your Volume Changed Abruptly

Mailbox providers expect predictable sending patterns from legitimate senders. Sudden spikes, whether up or down, are interpreted as either a compromised account or a list-buying sender, and the automatic response is increased filtering.

The pattern we see most often: a brand runs a flash sale or a Black Friday campaign that sends 5x the usual daily volume. The send itself goes out, but for the week after, inbox placement at Gmail drops by 15 to 25 points. The cause is not the sale itself. It is the spike pattern, combined with whatever engagement those incremental sends generated.

Fix: ramp volume rather than spike it. If a campaign is going to send meaningfully more than your baseline, split it across two or three sends within the day, or across two days if possible. Keep the daily volume within 2x of your rolling average when you can. If you must send a large campaign, ensure the segments receiving it are your highest-engaged cohort.

4. Your Complaint Rate Crossed a Threshold

Every mailbox provider has complaint rate thresholds. Cross them and your delivery degrades immediately.

Gmail's threshold is 0.3%. Yahoo enforces around the same, sometimes lower. Microsoft's threshold is higher in absolute terms but enforcement can be sudden and broad. Complaints in Klaviyo are the "mark as spam" clicks that users make in their inbox, which are reported back to Klaviyo through the ISP feedback loops.

The Klaviyo complaint dashboard usually undercounts, because not every ISP provides full feedback loop data. The true complaint rate can be 1.5x to 2x what Klaviyo reports. If your reported complaint rate is at 0.15%, your actual rate at Gmail might already be near threshold.

What triggers complaints: unclear sender identity in the From field, unclear unsubscribe paths, too-frequent sending to segments that did not opt in to that frequency, promotional content to subscribers who expected transactional mail, and re-engagement campaigns to cold lists.

Fix: audit the complaint rate in Klaviyo per flow and per campaign. The flows that generate the most complaints are usually the ones to adjust first. Make unsubscribe easier, not harder. Segment sending frequency by stated preference or by engagement behaviour. Stop sending to subscribers who have not engaged in 90 or more days.

5. Content or Links Are Flagging Filters

This cause is real but overdiagnosed. Most "spam filter" content rules that senders worry about are not actually applied at the major providers. Gmail and Microsoft filter based on behaviour and reputation far more than on specific words or phrases.

That said, there are patterns that genuinely cause filtering:

• Link reputation. Redirects through shortened URLs or third-party tracking domains can trigger filtering when those domains have poor reputation. If your Klaviyo account uses a shared tracking domain that another sender has compromised, your mail gets filtered alongside theirs.
• Image-to-text ratio that is too extreme in either direction. All-image emails with minimal text are flagged by filters that associate that pattern with image-based phishing. All-text emails with suspicious links can be filtered on link analysis alone.
• Encoded content or unusual HTML structures. HTML that does not parse cleanly, or that uses unusual encoding patterns, can trigger conservative filtering.

What tends to break in Klaviyo specifically: custom tracking domains that were set up once and then forgotten, and that have since been flagged for reasons unrelated to the current sender. If your Klaviyo tracking domain appears on URIBL or SURBL, your mail will filter regardless of everything else.

Fix: check your tracking domain against Spamhaus, SURBL, and URIBL. Send a test through a tool like Mail Tester or GlockApps to see specific content flags. Simplify email HTML where possible. Use a branded tracking domain rather than the Klaviyo default if you have not already.

6. Your IP Reputation Has Degraded

If you are on a shared pool, this is mostly out of your hands until Klaviyo rebalances. If you are on a dedicated IP, this is fully in your hands and the diagnostic path is specific.

Note that as a Klaviyo customer, you do not have direct access to Gmail Postmaster Tools IP-level data or to Microsoft SNDS for Klaviyo-owned IPs. What you can check yourself: Gmail Postmaster Tools domain reputation (if you have a branded sending domain), Spamhaus/SURBL/UCEPROTECT for your domain, and seed-test placement across major ISPs. For IP-level reputation signals on Klaviyo's pools, escalate through Klaviyo's deliverability team or use a monitoring tool that combines customer-visible signals with Klaviyo-authorised IP data.

What tends to break: dedicated IPs with sending gaps (IP reputation decays when you stop sending), dedicated IPs that are sending to dormant segments (pulls reputation down fast), shared pool IPs where Klaviyo has not yet moved a poor-performing sender out.

Fix: for dedicated IPs, maintain consistent daily volume, suppress dormant segments, and monitor reputation continuously. For shared pools, flag the issue with Klaviyo deliverability support and provide evidence from your own metrics. They do rebalance pools, but they need specific data.

7. Your List Has Permission Problems

This is the least common cause on its own, but it is often the underlying reason for several of the others. If any meaningful part of your list was acquired in a way that did not produce explicit, auditable opt-in, delivery will be worse than for lists that did. Purchased lists are obvious. Less obvious: lists acquired through partnerships, lists that were migrated from another tool without a re-permissioning step, and lists that were grown through contests or giveaways with unclear subscription terms.

The signs: higher complaint rates even when you are doing everything else correctly, spam trap hits you cannot explain, and deliverability that improves when you segment by list source and exclude the suspect sources.

Fix: segment by acquisition source if you have the data. Run re-permissioning campaigns on suspect sources with clear opt-in language. Suppress the segments you cannot re-permission. Accept that some revenue from those segments is not worth the deliverability cost they impose on the rest of your program.

Working Through the List

The order above is rough frequency ranked. In practice, most senders will find their issue in the first three causes. Authentication, list hygiene, and volume pattern changes are the dominant causes of Klaviyo deliverability incidents in practice.

Start with authentication, because it is the easiest to verify and often the actual cause. Move to list hygiene next, because it tends to be the slowest-moving but most durable fix. Check for volume pattern issues if something changed in your sending schedule recently. Only drill into content, IP reputation, and permission issues if the first three came up clean.