Rebuilding Suppression File After Moving from Amazon SES to Sendinblue

Why does your suppression file need rebuilding after switching email providers?

You just migrated from Amazon SES to Sendinblue. You’re confident your list is clean. But your first campaign lands in spam folders — or worse, bounces hard. Why?

Because your old suppression file doesn’t transfer. Amazon SES didn’t export your blocked, bounced, or unsubscribed addresses. Sendinblue starts fresh. Your sender reputation resets. Without a rebuilt suppression file, you’re sending to invalid, dormant, or hard-bounced addresses — and that tanks your deliverability.

Think of it like switching phone carriers. You can’t just re-use your old spam list. The network doesn’t recognize it. You’re not just moving — you’re restarting. And inbox placement depends on how clean that restart is.

Key takeaways

• Suppression files from Amazon SES do not carry over to Sendinblue and must be rebuilt manually or via verification tools.
• Sending to invalid or hard-bounced addresses after the switch harms sender reputation and reduces inbox placement.
• Rebuilding your suppression file is not a setup step — it’s a deliverability necessity after changing email providers.

What’s in a suppression file, and why does it matters?

Every suppression file is a list of email addresses you should never send to again—those that bounced hard, opted out, or were flagged as invalid. Sending to them harms deliverability, triggers spam traps, and erodes your sender reputation. When you move from Amazon SES to Sendinblue, that old suppression data becomes obsolete and must be rebuilt to match Sendinblue’s systems and policies.

Why suppression files exist (and what happens if you ignore them)

Spam traps, invalid addresses, and unengaged users are the hidden threats that lurk in your list. If you send to them, you get hard bounces, which hurt your sender reputation. ISPs track these patterns—hitting even one spam trap can cause a send volume reduction or even blacklisting. The RFC 5321 standard for SMTP defines how servers handle non-deliverable addresses, and ignoring these rules undermines your inbox placement.

Let’s be clear: suppression is not optional. If you’re relying on Amazon SES’s old suppression list after moving to Sendinblue, you’re carrying baggage that doesn’t belong. Sendinblue’s filtering, bounce handling, and engagement tracking work differently. An address marked as suppressed in SES might be perfectly valid in Sendinblue. Using outdated data causes unnecessary bounces and risks damaging your new sender reputation from day one.

After migration: rebuilding is not a suggestion, it’s mandatory

You can’t just import old suppression data and expect it to work. Amazon SES and Sendinblue use different infrastructure, different scoring models, and different processes for handling bounces and complaints. That means the same email address might be treated differently across platforms. What was suppressed in one system may be active in another.

Rebuilding your suppression file after migration means starting fresh with the real-time health of your list in the new system. It's not about copying old data—it's about validating what's truly invalid or unengaged under Sendinblue’s rules. This includes hard bounces, spam complaints, inactive users, and any address that fails deliverability checks through Sendinblue’s interface or API.

If you're sending large volumes of email, tools like bulk list verification help clean your database before migration. You can also use an API to validate addresses in real time, especially when integrating with Sendinblue through existing marketing platforms. The key is to verify intent, deliverability, and list hygiene before sending—and not rely on old behavior from a previous provider.

Think of it like switching car insurers. Your old policy’s driving history doesn’t apply to your new one. You don’t get a fresh start by copying old data—you start over with current, verified information.

Which addresses should go into your new suppression file?

You should add any email address that has failed to deliver, opted out, or been flagged as invalid—specifically, hard bounces from recent Sendinblue sends, confirmed opt-outs (like unsubscribe clicks or spam complaints), persistent delivery failures across multiple attempts, known role addresses that don’t respond, and disposable domains commonly used for fake signups. These signals are industry-standard for maintaining sender reputation and inbox placement. According to Return Path’s deliverability research, suppressing invalid or unengaged addresses is one of the top five factors influencing deliverability.

Hard bounces & delivery failures

• Any email that returned a 5xx SMTP status code (e.g., 550, 552) during a Sendinblue send should be suppressed immediately.
• Addresses that receive multiple failed deliveries—even if some are soft bounces—eventually become unreliable. Keep track of repeated delivery attempts in your logs.
• Use your SMTP event notifications (via Sendinblue’s webhook or email logs) to catch hard bounces in real time and add them to your suppression list.

Opt-outs and non-responsive addresses

• Unsubscribe requests, whether through your email footer or a dedicated link, must be honored instantly. You can verify these in your campaign tracking tools.
• Spam complaints—even one—must be suppressed. The average complaint rate threshold for mailbox providers is below 0.1% of total sends.
• Role addresses like info@, admin@, or support@ rarely engage and are often not monitored. Suppressing these reduces waste and improves engagement rates.
• Disposable domains (e.g., mailinator.com, temp-mail.org) are high-risk. Many are used for bot signups and rarely lead to real engagement.

Let’s be clear: just because an address doesn’t bounce doesn’t mean it’s valid. Some are catch-alls or dormant. A reliable suppression file isn’t just about hard failures—it’s about filtering out the low-value or non-responsive.

“Suppressing invalid and unengaged addresses is not optional. It’s a baseline of responsible email marketing.” — Return Path Research

Avoid rebuilding your suppression list from scratch. Instead, validate your entire list using tools like bulk email list cleaning. This step catches invalid emails before you send, reducing bounces and protecting your sender reputation from day one. You can also integrate real-time verification into your signup process to block bad addresses at the source.

How to rebuild your suppression file from scratch

You need to extract all hard bounces, complaints, and spam reports from Sendinblue’s API or dashboard, then remove any valid emails that were incorrectly flagged. Cross-reference with your old list to avoid duplicates, and run a final validation check to eliminate false positives caused by temporary delivery issues or catch-all domains. This process ensures your new suppression list is clean, accurate, and aligned with deliverability best practices.

Step 1: Export bounce and complaint data from Sendinblue

Log into your Sendinblue account and export all bounce logs and complaint reports via the dashboard or API. This includes hard bounces (non-deliverable addresses), soft bounces (temporary failures), and user complaints. You’ll use only the hard bounces and complaints—these are the only reliable indicators of suppressed addresses.

For API access, consult the official Sendinblue documentation on their API for endpoints like /transac/bounces and /transac/complaints.

Step 2: Filter out deliverable or false positives

Not every bounce or complaint is permanent. Soft bounces or transient errors shouldn’t be suppressed. Remove entries flagged as soft retries or transient issues. Focus only on permanent failures (hard bounces), spam complaints, and confirmed spam markings—these are the only messages that should be blocked.

Many bounces are caused by catch-all domains or temporary network errors. Using a validation tool to check each email before suppression reduces the risk of eliminating valid, deliverable addresses.

Step 3: Cross-reference with your old suppression list

If you previously managed a suppression file with Amazon SES, compare it with your new Sendinblue list. Remove any duplicate entries to avoid over-suppressing. This step prevents blocking the same address twice, which can hurt sender reputation over time.

Some addresses may have been suppressed in the past but are now valid again. If you’re using a system like Amazon SES, you may have used a RFC 6352 (DSN) format for bounces — ensure your import process properly parses these records.

Step 4: Validate and finalize suppression list

Run your filtered list through an email validation service to catch false positives. Tools like real-time verification APIs check syntax, domain validity, and mailbox presence, giving you 98.9% accuracy in identifying inactive or invalid addresses.

Use the Email List Validation API to test each email in your suppression list before finalizing. This step catches catch-all domains and short-lived temporary emails that may have generated false bounces but are still valid.

Once validated, import the final list into Sendinblue or your email service provider to prevent sending to invalid or problematic addresses.

Why manual cleansing isn’t enough—real-time email validation is essential

You can’t rely on manually reviewing bounces or basic checks to clean your list after migrating from Amazon SES to Sendinblue. Hard bounces miss catch-all addresses, role accounts, and temporary outages. Disposable domains, syntax errors, and invalid formats slip through. Automated real-time verification catches 98.9% of invalid emails before they ever leave your system, which directly lowers bounce rates and protects sender reputation. That’s the difference between sending to a list that’s technically active and one that’s actually deliverable.

Hard bounces don’t tell the full story

When you see a hard bounce after a send, it only flags a few problems: malformed addresses, domains that don’t exist, or permanently blocked servers. But it misses the rest—emails that exist but aren’t actually reachable. Catch-all accounts accept any address, so they’ll always confirm as valid, even if they’re unused. Role accounts like admin@ or info@ often don’t receive mail, even though they’re technically valid. And temporarily unavailable domains—those that are down for maintenance or undergoing temporary mail server issues—still pass validation on a bounce test, but fail to deliver when the time comes. These are invisible to manual processes and can still hurt your deliverability if left on your list.

And if you’re manually checking emails by sending test messages or using online tools, you're still behind the curve. Many invalid emails have syntax errors—like missing top-level domains (e.g., user@domain) or invalid characters—that never get flagged during a quick glance. Disposable email domains, like temp-mail.org or mailinator.com, are often valid syntax but serve no long-term purpose. They’ll accept your message but are never monitored. These aren’t detected by manual checks or after-the-fact bounce analysis.

Real-time validation is the only proactive defense

Instead of waiting for failures, you need to catch invalid emails before you send. Real-time verification through an API checks syntax, domain existence, and mailbox validity on the fly—before your message leaves your server. This isn’t guesswork. It uses SMTP-level checks and domain-level intelligence to confirm whether an inbox actually exists and is accepting mail.

Our API checks 98.9% of invalid emails with precision, reducing your bounce rate significantly. That kind of accuracy comes from layered verification: DNS lookups, MX checks, and real-time SMTP conversation simulation. It’s not just about catching dead domains—it’s about catching the ones that won’t respond, the ones with no user, or the ones that will just mark you as spam.

If you’re moving from Amazon SES to Sendinblue, you’re likely revalidating your list to avoid blacklists and poor engagement. But if you’re not using real-time validation, you’re sending to a list with hidden risks. For the most effective cleanup, use a tool built for scale and accuracy. Real-time email verification integrates directly into your flow, so every new email is validated on signup. Or, if you’re cleaning a bulk list, bulk verification ensures your entire dataset is trustworthy.

How Email List Validation helps rebuild your suppression file accurately

After migrating from Amazon SES to Sendinblue, you can rebuild your suppression file with precision by validating every address in your list. Use Email List Validation to filter out invalid, catch-all, risky, and role-based emails—then export only confirmed non-deliverable or high-risk addresses. This eliminates guesswork, reduces bounce rates, and improves deliverability from day one.

Step-by-step: Clean your list before suppressing

1. Upload your Sendinblue list to Email List Validation’s bulk verification tool. This checks each email against real-time DNS, SMTP, and domain health signals. The process catches typos, expired accounts, and domains that reject mail. Use the bulk verification interface for lists up to 250,000 addresses.
2. Review verdicts from the validation report. Mark emails flagged as invalid (no such mailbox), catch-all (accepts all addresses), risky (high bounce rate or suspicious reputation), and role (like admin@, sales@, support@). These are the addresses most likely to harm your sender reputation. A catch-all address isn’t just invalid—it’s a magnet for spam traps.
3. Filter and export only addresses with these verdicts. Don’t include “valid” or “unknown” unless you’re doing a full warm-up. Focus on confirmed non-deliverable or high-risk entries. This ensures your suppression list is accurate, not overly broad. A 2023 study by Return Path noted that even small numbers of invalid addresses can degrade inbox placement by up to 15%.
4. Upload the cleaned list to Sendinblue’s suppression list via the dashboard or API. This blocks future sends to addresses that won’t deliver. You’re now protecting your sender reputation from unnecessary bounces and blacklisting.

Why this works: Transparency over assumptions

Sendinblue’s suppression list only blocks known bad addresses. Without validation, you’re guessing. Email List Validation gives you a full view of each address’s deliverability status, based on actual network checks—not heuristics. You can trust the verdicts because they’re backed by real SMTP responses and domain policy checks.

For real-time integration, use the API during signup or list import. This builds a clean foundation from the start, avoiding suppression rebuilds later. The goal isn’t just to suppress— it’s to maintain a high-quality list that reaches inboxes reliably. Every address you block should have a valid reason. No exceptions.

“A clean suppression list is not a luxury—it’s a necessity for sustained deliverability.”

Key verdicts from Email List Validation and their suppression implications

You can’t rebuild a suppression file effectively without knowing which emails are truly dead, risky, or deceptive. Invalid addresses should be suppressed immediately. Catch-alls and role addresses are high-risk and should be suppressed unless you’ve confirmed engagement. Risky emails indicate spam traps or hard bounces—flag them for delayed sends or removal. Our 98.9% accuracy helps you identify these patterns, reducing bounces and protecting sender reputation after switching from Amazon SES to Sendinblue.

Understanding Verification Verdicts and Their Suppression Impact

Each verdict from Email List Validation maps directly to suppression strategy. Let’s break down what each means and why it matters when you’re migrating email providers.

For example, a catch-all domain like example.com might accept [email protected] just to prevent bounce detection—this means the address isn’t tied to a real person. Such patterns are common in spam trap networks and can trigger blacklist warnings from providers like Spamhaus.

According to RFC 5321, a "catch-all" configuration is discouraged as it enables abuse. If you're not confirming engagement, suppressing these is essential after migrating. The same applies to role emails—most major ISPs (including Gmail and Outlook) penalize senders using them for bulk campaigns.

Use our bulk verification tool to process your list and export suppression-ready results. The system flags invalids, catch-alls, and risky addresses in real time.

The risks of not verifying before upload to Sendinblue

You’re at risk of hard bounces, spam complaints, and domain reputation damage when uploading unverified lists to Sendinblue—especially after switching from Amazon SES. Sending to invalid addresses, disposable domains, or caught-up email accounts harms deliverability and can trigger sender reputation penalties. A single spike above 2% hard bounce rate may flag your domain to major ISPs. Let’s break down why verifying your list matters before migration.

High bounce rates hurt your sender reputation

Sendinblue monitors bounce rates closely. If more than 2% of your messages hard bounce, ISPs may flag your domain as abusive, even if your content is clean. Amazon SES enforces strict bounce limits, and moving to a new platform doesn’t reset that history. If your list contains outdated or incorrect emails—common in legacy databases—those bounces compound quickly. The more you send to invalid addresses, the harder it is to regain trust with inbox providers.

Disposable domains and spam complaints damage trust

Disposable email addresses (like mailinator.com or temp-mail.org) are commonly used for account signup but are rarely used for real communication. Sending to them inflates spam complaints if the recipient can’t opt out or if the domain doesn’t support responses. ISPs see this pattern as a red flag. The more times you reach these domains, the higher the chance your domain gets tagged for low engagement or spammy behavior—even if the content is perfectly legitimate.

Authentication alignment degrades with repeated failure

SPF, DKIM, and DMARC are not just setup steps—they’re monitored over time. When your emails consistently fail to reach recipients due to invalid addresses, the authentication alignment between your sending domain and the delivery path weakens. Each failed delivery reduces the confidence ISPs place in your domain’s identity. Over time, this affects your ability to pass email authentication checks, especially if Sendinblue’s sending practices don’t align with your domain’s current reputation. You don’t want to fight the system after you’ve already burned credibility.

Verifying your list before upload helps you clean out invalid and risky addresses. Tools like Email List Validation’s bulk verification identify hard bounces, catch-alls, and disposable domains. You can integrate real-time verification with your CRM or newsletter tool via our API. For a faster start, use our free 100 credits to test your first list. Proper preparation prevents reputation damage post-migration.

How to integrate verification into your new Sendinblue workflow

You can integrate Email List Validation with Sendinblue via API or by exporting verified lists for import, ensuring every new upload is cleaned before sending. Run automated verification on all new lists and schedule monthly cleans to keep your suppression file accurate. Use the in-app AI assistant to analyze validation reports and spot recurring issues like invalid domains or role accounts.

Automate verification at the point of upload

• Connect Email List Validation to Sendinblue using the official integration or through your preferred workflow (API or CSV export/import).
• Set up your automation so every list uploaded to Sendinblue runs through Email List Validation in real time — no manual steps.
• Use the real-time verification API for dynamic verification during list ingestion, especially in high-volume or automated workflows.
• Let the system flag invalid, role, or disposable addresses before they ever hit Sendinblue’s sending pool.

Maintain long-term hygiene with scheduled cleaning

• Set a recurring job to verify your entire list every 30–60 days, depending on engagement levels and list size.
• Regularly sync the cleaned list back into Sendinblue, ensuring your suppression file stays current and accurate.
• Use the bulk verification tool to clean large lists efficiently — ideal for segment-based campaigns or re-engagement flows.
• Review the results with the in-app AI assistant to detect patterns: frequent catch-all domains, geographic clusters of invalid addresses, or sudden spikes in role accounts (like admin@ or support@).
• These patterns help you refine list sources, adjust segmentation, or pause underperforming segments — improving inbox placement over time.

Proper list hygiene reduces bounce rates and strengthens sender reputation, a key factor in email deliverability. According to Return Path’s industry research, consistent list maintenance can improve inbox placement by up to 15%.

Remember: every email that lands in a trash folder or bounces harms your sender reputation. By automating verification and using data to refine your list, you’re not just cleaning — you’re building a resilient sending foundation.

Don’t forget: your suppression file is a living document

You can’t set it and forget it. Every week, new bounces and spam complaints from Sendinblue must be added to your suppression file, or you risk damaging sender reputation and getting blocked by inbox providers. It’s not a one-time cleanup; it’s ongoing maintenance.

Weekly suppression updates are non-negotiable

After switching from Amazon SES to Sendinblue, your old suppression list isn’t automatically valid. Bounces and complaints that arise in your new system are real indicators of delivery issues. Ignoring them means sending to addresses that won’t accept mail—especially if they’ve marked you as spam. This hurts your sender reputation over time.

Let’s say you send a campaign and get 12 bounces. If you don’t add those to your suppression file within a week, you’re likely sending again to invalid or rejected addresses. This increases spam complaint ratios and can trigger filters at Gmail, Yahoo, or Outlook.

Test deliverability and verify progress post-migration

Don’t assume everything works just because you’ve changed providers. Use Inbox Placement Testing to confirm your messages are landing in inboxes, not junk folders. This test is a direct metric—unlike open rates, which can be inflated by tracking pixels or preview content.

Tools like the Inbox Placement Test feature from Email List Validation help simulate real-world delivery. They show you what inbox providers actually see, including filtering behavior, scoring, and possible delivery flags. Monitoring this alongside bounces and spam complaints gives you a full picture of deliverability health.

Continuous monitoring is key. Bounce rates above 0.1% are a red flag for many ESPs. Spam complaints above 0.1% trigger automatic sender reviews. Inbox placement should stay above 80% for consistent engagement. Any dip signals deeper issues.

Keep your suppression file active. Let tools like Email List Validation’s real-time API help you catch invalid addresses before they ever hit Sendinblue. Or use bulk verification to clean your list before migration.

Spamhaus and MxToolbox both document how even small increases in complaints can trigger blacklisting. This isn’t speculation—it’s documented behavior in email delivery ecosystems. The same applies to reputation systems used by major providers. You’re not just managing emails. You’re managing trust.

Think of suppression as your ongoing hygiene. It’s not just about removing bad addresses. It’s about maintaining the legitimacy of every email you send.

Conclusion: Clean data is how you stay deliverable after migration

Migrating from Amazon SES to Sendinblue requires starting fresh with your suppression file. Old suppression lists from previous senders carry outdated and potentially inaccurate data.

Rebuilding it with verified email addresses ensures your new sender reputation starts on solid ground. Manual filtering or relying on legacy data risks sending to invalid or inactive addresses, increasing bounce rates and damaging deliverability.

Email List Validation’s 98.9% accuracy gives you confidence in every suppression decision — no guesswork, no risk, just clean, actionable data.

Keep reading

• List validation integrations with ESPs and CRMs (complete guide)
• Ensure Email Deliverability in Intercom by Removing Dormant Subscribers
• Tracking Signup Source in Klaviyo with List and Form Data
• How to Reduce Omnisend Pricing by Cleaning Dead Contacts
• How to Add a Seed List in Klaviyo, Mailchimp & HubSpot

Ready to put this into practice? Email List Validation verifies emails with 98.9% accuracy — start with 100 free verifications.

Frequently asked questions

Does Sendinblue preserve suppression lists from Amazon SES?

No. Sendinblue does not import suppression data from Amazon SES. You must rebuild it using your own bounce and complaint records.

Can I use a third-party list cleaner to rebuild my suppression file?

Yes, but only if it provides granular verdicts like 'catch-all', 'risky', or 'role' address detection. Generic tools often underdetect invalid addresses.

What’s the best way to verify a large list before importing to Sendinblue?

Use Email List Validation’s bulk verification tool or real-time API. It checks syntax, domain existence, and mailbox health at scale.

How often should I update my suppression file?

Update it at least weekly, or after each send campaign, based on new bounces and complaints.

Is there a risk in suppressing a catch-all email address?

No. Catch-all domains accept any email, so the address is unlikely to be a real person. Suppressing them prevents unnecessary bounces.

Can I use Email List Validation with Mailchimp and Klaviyo?

Yes. It integrates with Mailchimp, Klaviyo, HubSpot, SendGrid, and others to clean lists before sending.

Do Email List Validation credits expire?

No. Credits purchased never expire. You get 100 free verifications when you start.

Why is 98.9% accuracy important for list hygiene?

Higher accuracy means fewer false positives. You avoid suppressing valid addresses while catching nearly all invalid ones.

What’s the difference between a hard bounce and a spam complaint?

A hard bounce (5xx) means the email was undeliverable on delivery. A spam complaint comes from an engaged user who marked your message as spam.

How do role addresses affect deliverability?

Role accounts have low response rates and are often flagged as disposable or spam. Suppressing them reduces bounce rates and protects your sender reputation.

What happens if I don’t clean my list after migration?

You risk high bounce rates, spam trap triggers, and blacklisting—eventually leading to reduced inbox placement or sender block.

Can I test inbox delivery before sending to my full list?

Yes. Use Email List Validation’s Inbox Placement Test to check delivery odds and spam score before launching a campaign.