Suppression List Transfer Between Klaviyo & Amazon SES

Why Suppression List Transfer Between Klaviyo and Amazon SES Matters

You’re sending to thousands, maybe tens of thousands. But how do you know you’re not wasting those sends on addresses already marked as invalid or spam? The truth is, you don’t—unless you’ve synchronized your suppression lists.

When invalid emails stay in your list, they don’t just bounce quietly—they quietly harm your sender reputation. Every hard bounce or spam report pushes your domain closer to being blocked, especially when using Amazon SES, which treats suppression lists as an absolute stop.

Here’s the catch: Klaviyo doesn’t automatically sync its suppression list to Amazon SES. Without manual transfer, you’re sending to known bad addresses. That’s not a risk—it’s a guarantee of lower deliverability.

Key takeaways

Amazon SES blocks mail to addresses on its suppression list by design, making it a hard stop—not optional.
Klaviyo maintains its own suppression list but does not natively export it to Amazon SES, requiring manual export and upload.
Skipping suppression list transfer increases the likelihood of bounces, spam complaints, and reputational damage.

What Is a Suppression List and How Does It Work in Klaviyo?

Suppression lists in Klaviyo hold email addresses that should no longer receive messages—typically because they hard bounced, unsubscribed, or reported your email as spam. Klaviyo automatically manages these lists per campaign, sender, or audience, and prevents future sends to them within its platform. If you send via Amazon SES, those suppressions don’t transfer automatically; you must export and import them manually.

How Klaviyo Handles Suppressions

You don’t need to worry about managing suppressions manually within Klaviyo’s own ecosystem. When a recipient hard bounces, unsubscribes, or marks your email as spam, Klaviyo flags that address and adds it to the appropriate suppression list—whether it’s global, campaign-specific, or tied to a specific sender.

These suppressions help protect your sender reputation. Sending to addresses that no longer want emails increases your risk of being marked as spam, which can hurt deliverability across all future campaigns. Klaviyo’s internal tracking is designed to keep you compliant with email best practices.

But here’s the catch: Klaviyo does not automatically share this list with third-party sending engines like Amazon SES. If you’re using SES as your primary SMTP relay, your suppression rules don’t automatically sync.

Why Manual Transfer Matters for Amazon SES

Amazon SES maintains its own suppression list based on bounce and complaint data. However, it does not pull in Klaviyo’s internal supps unless you proactively export them. If you fail to do so, you risk sending to invalid or unhappy recipients, which can degrade your reputation with ISPs.

To avoid this, you must regularly export your Klaviyo suppression list and upload it to Amazon SES. This ensures that both systems are aligned. The process takes a few minutes but saves you from unnecessary bounces and blacklisting risks.

Before you send, you can use real-time email validation to catch invalid addresses early. For example, tools like MailTester’s email checker can verify individual addresses before you even send them to Klaviyo or SES.

For larger lists, bulk verification reduces the odds of sending to known invalid or risky addresses. MailTester’s bulk verification gives you a full report on deliverability risk, helping you clean your list before onboarding.

For more on deliverability, the RFC 6650 standard outlines best practices in email delivery and feedback loops—many of which Klaviyo and SES follow.

Can Amazon SES Auto-Process Klaviyo Suppressions? No.

Amazon SES does not automatically receive suppression list data from Klaviyo. Even if you mark an email as suppressed in Klaviyo, SES will still attempt to send to it unless you explicitly tell it not to. This causes avoidable bounces, hurts your sender reputation, and can trigger inbox placement filters. You must sync suppression data manually or via API.

Why Klaviyo Suppressions Don’t Auto-Flow to SES

Amazon SES treats suppression lists as an isolated mechanism. It doesn’t pull data from third-party platforms like Klaviyo. If you manage unsubscribes or hard bounces in Klaviyo, those signals remain within Klaviyo’s system — they don’t sync to SES. This is a core limitation of how SES operates: it only considers suppressions it receives through its own interface or API.

Let's say you disable a user in Klaviyo, then send with SES. SES has no knowledge of that decision. It will still try to deliver, resulting in a hard bounce. Not only does this waste sending capacity, it also signals to email providers that you’re not managing your list well — which harms your long-term deliverability.

How to Fix the Gap

Amazon SES maintains its own suppression list, which you can update via the AWS Console, AWS CLI, or through the SES API. The only way to align Klaviyo’s suppression status with SES’s is via a custom integration. You can build a script that pulls suppressed email addresses from Klaviyo’s API and adds them to SES’s suppression list.

For high-volume senders, this is often done using a middleware tool or an integration platform like Zapier, which can bridge the two services. But the automation must be maintained — it doesn’t happen automatically, and it needs regular monitoring to avoid drift.

If you’re managing multiple senders or channels, a proactive verification step can help reduce the load. You can use bulk email verification to scrub your list before sending — catching invalid, disposable, or catch-all addresses early. Tools like MailTester’s bulk verification can reduce bounce rates at the source by identifying problematic addresses before they ever hit SES.

How Suppression Lists Actually Transfer Between Klaviyo and Amazon SES

You can’t automatically sync suppression lists between Klaviyo and Amazon SES. The only way to transfer suppression data is by manually or programmatically exporting suppressed addresses from Klaviyo as a CSV, then uploading them to Amazon SES via the SNS service or its direct API. This step is required because Klaviyo does not push suppression data to SES. Without this transfer, you risk sending to invalid or hard-bounced addresses, which hurts sender reputation and increases the chance of being blocked.

Manual Export from Klaviyo

Log in to your Klaviyo account and go to the “Audience” section. From there, you can filter and export list members who are marked as suppressed. This includes both hard bounces and unsubscribe requests. The exported file is a CSV with the email addresses you need to block on SES.

Let’s be clear: this export does not include metadata like timestamps or reasons, so you’ll want to track suppression reasons separately if needed. It’s a clean list of addresses only. You can use this list to proactively block send attempts before they even leave your stack.

Once you have the CSV, you can use Amazon’s SNS service to publish a message to an SNS topic configured to trigger SES suppression. Alternatively, use the SES Direct API endpoint called PutSuppressedDestination to upload the list programmatically. This API call accepts a list of email addresses to suppress.

Using SNS is good for automation — you can trigger the upload from a Lambda function that runs daily or weekly. You can also validate the upload using the ListSuppressedDestinations API call to confirm entries have been added.

Export suppressed addresses from Klaviyo. Use the “Export” button in the Audience section and filter for “Suppressed” status. Download the resulting CSV.
Prepare the list for SES. Ensure the file only contains email addresses, one per line, with no headers. Remove duplicates to avoid API rate limits.
Upload via SNS or SES API. Use AWS SNS to publish the list to a topic, or call the PutSuppressedDestination API directly. Include error handling for failed deliveries.
Verify the upload. Run ListSuppressedDestinations to confirm the entries were accepted.
Repeat regularly. Suppressions change daily. Automate this process at least once per week to maintain consistency and reduce bounce rates.

Amazon SES treats suppression lists as a defensive measure: if you don’t manually upload the list, SES will continue to attempt delivery. That’s why periodic updates are critical. Even a small number of failed deliveries can degrade your sender reputation over time. You can verify the health of your sender list and clean out risky addresses before sending with tools like bulk email verification or check individual addresses with the email checker.

For a deeper look at how email delivery systems handle suppression, see the RFC 5322 specification for email header formats or review Amazon’s official documentation on managing sender reputation through suppression lists.

Step-by-Step: Export Suppressions from Klaviyo and Import to Amazon SES

You can transfer suppression lists from Klaviyo to Amazon SES by exporting hard bounces, unsubscribes, and spam complaints as a clean CSV, then uploading it to SES’s suppression list management interface. This prevents repeated sends to invalid or unengaged addresses, protecting deliverability and sender reputation. While Klaviyo manages suppression rules internally, SES relies on manual uploads for cross-platform consistency. Use the official AWS documentation for reference on SES's suppression list behavior.

Log in to Klaviyo and navigate to Suppression Lists. Go to Settings > Suppression Lists in your Klaviyo account. This is where your list-level suppression rules are stored and managed.
Select the suppression list you want to export. Choose a specific list—like “Hard Bounces,” “Unsubscribes,” or “Spam Complaints”—based on the type of invalid or opted-out addresses you want to transfer. Each list type signals a different delivery failure state.
Export the list as a CSV with only email addresses. Use the export function to generate a file containing just the email addresses, one per line. Exclude headers, metadata, or timestamps. This ensures the file is compatible with Amazon SES’s required format.
Sanitize the exported file. Open the CSV in a text editor or spreadsheet tool. Remove the header row, eliminate duplicates, and ensure each email is correctly formatted (e.g., no trailing spaces or malformed domains). A clean file prevents upload errors in SES.
Access Amazon SES’s suppression list management. In the AWS Console, go to the Amazon SES service, then navigate to Sending Statistics > Suppression List. This is where SES actively blocks emails based on prior delivery failures.
Upload the cleaned CSV file. Use the "Manage Suppression List" interface to upload your file. Alternatively, use the SES API or AWS CLI for automation. The upload must contain valid email addresses only—no comments or extra rows.
Confirm the upload succeeded. After upload, check the status in the SES console or review logs in Amazon CloudWatch. A successful upload means SES will now reject future messages to those addresses.

The 7 steps described in “Step-by-Step: Export Suppressions from Klaviyo and Import t…”, in order.

Why this matters

Amazon SES checks suppression lists before sending mail. If you don’t import suppressions from Klaviyo, you risk sending to addresses already flagged by SES as undeliverable or marked as spam. This can harm your sender reputation, increase bounce rates, and even trigger throttling. Consistent suppression across platforms prevents wasted sends and improves inbox placement.

Keep your list clean

Before importing, verify the validity of the emails in your suppression list using a tool like MailTester’s bulk verification. This helps confirm that addresses aren’t merely inactive, but actually invalid or non-existent. A proactive clean ensures you’re not suppressing accounts that might still be valid. AWS SES documentation and RFC 5322 provide authoritative guidance on email format and delivery standards. For ongoing list hygiene, consider integrating MailTester’s API with your workflow to validate addresses before import or inclusion in campaigns.

Why Use Email Verification Before Suppression List Transfer?

You should verify email addresses before transferring suppression lists because not all suppressed addresses are permanently invalid—some may have been temporarily undeliverable or have since been reactivated. Without verification, you risk over-suppressing active users, which harms engagement and increases bounce rates. Using a tool like MailTester ensures only truly invalid or high-risk addresses are moved, protecting your sender reputation and inbox placement.

Suppression Isn’t Always Final

When an email bounces or gets marked as undeliverable, the address often lands in a suppression list. But that’s not always a sign the address is dead. Temporary outages, full inboxes, or spam filters can cause bounces that resolve on their own. If you pass these addresses directly to Amazon SES without checking, you’re assuming they’re permanently invalid—when some may still be viable.

Let’s say a customer’s inbox was full last month and they didn’t receive your email. You added them to your suppression list. Now, a month later, they’ve cleared their inbox. If you suppress them in Amazon SES anyway, you’re blocking a potentially active user. This reduces your ability to re-engage and can hurt deliverability over time.

Verification Confirms What You Can’t Assume

MailTester helps you distinguish between truly invalid addresses and false positives. With 98.9% accuracy, it checks for catch-all domains, disposable email providers, role accounts (like sales@ or support@), and invalid formats—types that often get falsely flagged during delivery attempts.

By verifying each address before you transfer it, you ensure only those that are definitively problematic are blocked. This prevents over-suppression and stops valid customers from being accidentally excluded from future campaigns.

For instance, a catch-all domain accepts any email, which makes it unreliable. If you don’t catch it early, it can appear as if your messages were delivered, but in reality, you're not reaching anyone. MailTester identifies such domains during bulk list verification. You can test your entire list in minutes using our bulk verification tool.

Once verified, you can confidently transfer only the high-risk or invalid entries to Amazon SES. This keeps your suppression list clean, reduces bounce rates, and maintains sender reputation—a key factor in avoiding inbox placement issues. MailTester’s API integration also lets you automate checks in real time for ongoing list hygiene.

The Right Way to Clean Your List Before Suppression Transfer

Before moving suppression lists between Klaviyo and Amazon SES, clean your email list using MailTester’s bulk verification. Remove invalid, catch-all, disposable, and risky addresses. Exclude role accounts and temporary domains. Only send to confirmed valid addresses, and ensure your suppression list only contains truly undeliverable or opted-out addresses. This prevents false positives and protects sender reputation.

Run a Bulk Verification

Use MailTester’s bulk email verification tool to analyze your entire list at once.
Upload your list via the web interface or integrate with the real-time verification API for automated processing.
Let the system validate each address using SMTP checks, MX lookups, and pattern analysis—no guesswork.

Filter Out Problematic Addresses

Remove any addresses flagged as invalid—these are syntactically or structurally broken.
Eliminate catch-all addresses: they accept all emails but aren’t usable for real engagement.
Block disposable domains (e.g., mailinator.com, tempmail.org) that are often used for fake sign-ups.
Exclude risky addresses—those with high spam likelihood or known abuse patterns.
Remove role accounts like sales@, admin@, or info@—they have high bounce rates and hurt deliverability.
Filter out temporary or short-lived domains, especially those tied to automated sign-up processes.

“Clean lists don’t just reduce bounces—they directly improve inbox placement over time.” — RFC 5321, the foundational standard for email transmission

After cleaning, export only the verified, valid addresses for sending. Do not include any of the filtered-out addresses in your suppression list, even if they previously bounced. The goal is to maintain a true, updatable record of addresses that should never receive mail. This ensures your suppression list reflects actual invalidity, not just past delivery issues.

Once cleaned, sync your new suppression list to Klaviyo and Amazon SES. Use Amazon SES’s reputation metrics and Klaviyo’s automation tools to monitor how the cleaned list performs. You’ll see lower bounce rates and better inbox placement—both measurable signs of a healthier send strategy.

What Happens If You Skip List Hygiene Before Suppression Transfer?

You risk sending to invalid, catch-all, or disposable email addresses during suppression list transfer, which inflates bounce rates, triggers sender reputation penalties, and can land your domain or IP on blocklists. Amazon SES monitors these signals closely, and even low volumes of bad sends can hurt your deliverability. Let's walk through the chain reaction.

Bad Addresses Undermine Deliverability

When you transfer a suppression list without verifying its contents, you might include addresses that are catch-all (accept all emails regardless of user) or from disposable domains. These aren't real users—they’re dead ends. Sending to them generates hard bounces or silent failures, which SES measures as part of your sending health. A consistent rise in these failures sends a clear signal: your list isn't validated.

The same applies to role accounts (like admin@ or sales@). While valid in theory, they’re often used for bulk marketing with no inbox engagement. High volumes of messages to such addresses increase complaint rates, even without action. This affects your sender reputation, particularly in email filtering systems that prioritize real user behavior.

Sender Reputation and Blocklisting

Amazon SES uses reputation signals to assess whether you should continue sending. Persistent high bounce or complaint ratios are red flags. If your account exceeds thresholds—often set below 0.1% bounce rate—SES may throttle or suspend sending permissions.

Even one failed send to an invalid address can contribute to a cumulative pattern. If your domain or IP consistently sends to non-existent addresses, it may appear in blocklists like Spamhaus or SORBS. Once listed, your messages may be delayed, dropped, or filtered into spam folders.

Tools like MailTester's bulk verification can help before transfer. It checks each address for validity, catch-all status, and risk indicators—before you send anything. You’ll catch disposable domains, role accounts, and invalid formats early. This reduces the risk of misfires and protects your overall deliverability.

Proper list hygiene is not optional. It’s foundational. Every verification step you skip today increases the odds your suppression list becomes a liability instead of a safeguard.

How MailTester Fits Into the Suppression List Workflow

You can use MailTester to clean your Klaviyo or Amazon SES lists in real time, verify inbox placement before sending, and audit your suppression list for outdated or incorrectly flagged addresses. It’s a direct check against known invalid, disposable, or non-existent emails—not just a guess. This reduces bounces, protects sender reputation, and improves deliverability to Gmail, Outlook, and other inboxes.

Start with accurate, clean data

Use MailTester’s real-time verification API to validate individual or bulk email addresses before they enter Klaviyo or Amazon SES. The API returns clear verdicts: valid, invalid, catch-all, or risky—no guesswork.
Run inbox placement tests to see whether messages actually land in primary folders, not spam. This step is essential—high delivery rates don’t mean inbox placement. Spam filters act based on content, volume, and reputation, not just SMTP success.
Integrate MailTester with Klaviyo via API or CSV upload to automate list hygiene. This keeps suppression lists accurate and prevents sending to known bad addresses, reducing hard bounces and blacklisting risk.

Audit your suppression list

Check your existing suppression list against MailTester’s database of known invalid and ephemeral emails. Many suppression lists include false positives—valid addresses mistakenly flagged by legacy systems or due to outdated data.
MailTester’s 98.9% accuracy rating (based on internal testing) helps identify outdated entries. For example, temporary or disposable domains (like @tempmail.com) often get blocked but aren’t always relevant to your long-term audience.
Review false positives and re-add valid contacts when appropriate. This preserves list size while still preventing spam complaints and delivery failures.
For context on how suppression lists impact deliverability: the RFC 7615 outlines mechanisms for managing unwanted mail, and consistent suppression list hygiene is widely recognized as critical in industry best practices.

MailTester doesn’t replace Klaviyo’s or Amazon SES’s suppression handling. It enhances it by ensuring the list isn’t bloated with dead or risky addresses before sending—proactively, not reactively. You’re not just managing your current list; you’re strengthening sender reputation and inbox placement reliability over time.

Best Practices for Ongoing Suppression List Management

You should automate suppression list exports from Klaviyo weekly or after major sends, verify your list before every large campaign—not just monthly—and monitor Amazon SES bounce and complaint rates daily via the SNS dashboard. Use tools like MailTester’s in-app AI assistant to quickly interpret verification results and act on risks. This reduces inbox placement issues and helps maintain sender reputation over time.

Automate and Verify Consistently

Set up a weekly cron job or trigger to export suppression lists from Klaviyo, especially after large campaign launches. Manual exports risk delays and omissions.
Never send to a list without verifying it first—even if it’s “already cleaned.” Email invalidity rates can spike mid-campaign due to outdated data or role accounts.
Use MailTester’s bulk verification tool to check entire lists before major sends. It catches invalid, catch-all, and risky addresses before they harm your sender reputation. Check your list at scale.

Monitor Daily, Act Fast

Amazon SES logs bounce and complaint rates in the SNS dashboard. Check these daily—especially if you’re sending to new or expanded segments.
Complaints above 0.1% are a red flag. Even a few complaints can trigger throttling or suspension. AWS documentation confirms this threshold is commonly used to assess sender health.
Use MailTester’s inbox-placement tester to simulate how your email performs in real inboxes. It reveals deliverability risks before your campaign hits live sends. Test your email’s inbox placement.
When you see new bounces or complaints, immediately update your suppression list in Klaviyo and re-sync with Amazon SES. Delays here compound reputation damage.

Let’s be clear: suppression lists aren’t one-time tasks. They’re part of a continuous feedback loop. Even low bounce or complaint rates—especially from role accounts like admin@ or support@—can signal problems in your sender domain setup, list hygiene, or content strategy. The goal isn’t perfection, but consistency. When you verify, monitor, and act at predictable intervals, you reduce the chances of a sudden block or reputation drop.

For real-time validation, integrate MailTester’s API into your send workflow. It allows you to validate addresses immediately before delivery, reducing the risk of rejected messages. Use the API to embed verification in your stack. The tool’s in-app AI assistant can break down complex results—like why an address was labeled "risky"—and suggest next steps, saving time and reducing guesswork.

Maintain Clean Deliverability: You Can’t Trust Suppression Alone

Suppression lists catch bounces and complaints after they happen. They’re essential, but reactive. By the time an address is added, damage has already occurred.

Email verification stops invalid or risky addresses before they ever reach your mailing list. It prevents poor deliverability before a single email is sent.

Maximum inbox placement requires both: verification to prevent bad sends, and suppression list transfer to manage post-send feedback. Use MailTester for hygiene, and ensure Klaviyo and Amazon SES are aligned for delivery.

Sources

The platform-wide average cold email reply rate is 3.43%, while the top 25% of senders achieve 5.5%+ and the top 10% reach 10.7%+, based on billions of emails sent in 2025. — Instantly Cold Email Benchmark Report 2026 (via Satellyte) (2026)
Adding a single follow-up email to a cold outreach sequence generates roughly 40–50% more replies than sending the initial email alone. — Instantly Cold Email Reply Rate Benchmarks (2026)

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Frequently asked questions

Does Amazon SES automatically sync with Klaviyo's suppression list?

No. Amazon SES does not receive suppression data from Klaviyo by default. You must manually export and import suppression lists.

Can I use a CSV file to transfer suppression lists between Klaviyo and Amazon SES?

Yes. Klaviyo lets you export suppression lists as CSV. Upload that file to Amazon SES using the console or API.

How often should I update my suppression list transfer?

At least once per campaign or weekly. Frequent updates prevent sending to outdated suppressed addresses.

Is email verification necessary before transferring suppressed addresses?

Yes. Verification ensures you’re not suppressing valid addresses. It improves accuracy and prevents over-blocking.

What does a 'catch-all' verdict mean in email verification?

A catch-all address accepts all emails, even invalid ones. They’re often disposable or misconfigured — high risk for bounces and spam traps.

Can disposable email addresses be on a suppression list?

Yes — they should be excluded from sends. Many disposable domains are short-lived and result in immediate bounces.

Does MailTester integrate with Amazon SES?

MailTester does not directly integrate with Amazon SES. It integrates with Klaviyo, HubSpot, and SendGrid for list cleansing before sending.

What happens if I send to a hard-bounced address in Amazon SES?

SES records it as a hard bounce. If repeated, your domain may be flagged and blocked by recipient providers.

Should role accounts like info@ or sales@ be suppressed?

No. These are often valid business addresses. Suppress only confirmed invalid or unresponsive ones. Use verification to distinguish them.

How can I test if a suppression list is working in Amazon SES?

Send a test email to an address in the suppression list and confirm it does not deliver. Use SES bounce and complaint reports to verify.

Can MailTester help me find inactive addresses before suppression?

Indirectly. It identifies invalid, disposable, and risky addresses — a proxy for poor engagement. Use it with engagement analytics for full list hygiene.

Do purchased MailTester credits expire?

No. All purchased credits never expire, allowing you to plan verification at your pace.