How do Amazon SES and SendGrid actually handle bounces and complaints?

You send a campaign. A few days later, open rates dip. Deliverability metrics stall. Then you dig into the logs—only to find bounces and complaints piling up. Not knowing when or how they were detected can cost you inbox placement and sender reputation.

Both Amazon SES and SendGrid offer feedback loops (FBLs) and bounce notifications, but the real difference lies not in whether they detect issues—but how fast they tell you. One process waits. The other acts immediately.

Key takeaways

  • SendGrid’s complaint and bounce webhooks update in minutes; SES relies on SNS message processing, which introduces delays.
  • Faster detection of bounces and complaints enables earlier list hygiene, directly improving long-term sender reputation.
  • While both platforms provide FBLs and bounce notifications, SendGrid’s real-time delivery to webhooks gives it a measurable edge in responsiveness.

What happens when an address bounces on Amazon SES?

When an address bounces on Amazon SES, the system categorizes it as either a hard bounce (permanent failure) or a soft bounce (temporary failure). Hard bounces—like invalid email syntax or non-existent domains—are flagged in SNS notifications with a Type value of 'Permanent' and a Message field explaining the reason. After 24 hours, SES automatically blocks hard-bounced addresses from future sends, but only if you’ve enabled bounce handling rules. This prevents immediate reputation damage, but repeated failures across multiple addresses will degrade your sender reputation over time. You must parse SNS notifications and manage invalid addresses manually unless you automate with a tool like MailTester.

Hard bounces are actionable via SNS—unless you miss the signal

Amazon SES sends hard bounce notifications through SNS with structured data, including the recipient address, bounce type, and a human-readable reason (e.g., "User unknown" or "Mailbox unavailable"). The 'Type' field clearly distinguishes permanent failures from temporary ones, allowing you to act on invalid addresses. However, unless you’re actively monitoring and processing SNS messages, these signals can go unnoticed. Without a system to track and remove failed addresses, your list grows stale, increasing your bounce rate and risking delivery issues.

You can’t rely on SES alone to protect your deliverability

SES does not automatically clean your list, even after marking an address as hard bounced. That responsibility falls on you. If you send to 10,000 addresses and 500 hard bounce, you need to identify and remove those 500—otherwise, they’ll keep counting against your performance. A single hard bounce doesn’t hurt reputation, but consistent or large-scale failure does. According to RFC 6521, high bounce rates (generally above 0.5%) correlate with email filtering and delivery throttling. You won’t get a warning until it’s too late.

Manual processing is inefficient, especially at scale. Tools like MailTester simplify this: you can bulk verify your list before sending to catch invalid addresses early, reducing bounces before they happen. Use the bulk verification feature to identify risky, invalid, or disposable emails before hitting SES or SendGrid. The API version lets you validate in real time as you collect data. And if you're testing deliverability, the inbox placement tester shows how your message lands in real inboxes—before you send. With these tools, you’re not waiting for bounces to fix problems. You’re preventing them.

How does SendGrid handle bounces and complaints in real time?

SendGrid delivers bounce and complaint notifications instantly via webhooks, sending structured JSON data—like type, email, reason, and timestamp—within minutes of detection. This real-time stream lets you react fast, scrub invalid addresses, and reduce inbox placement risks before they impact your sender reputation. Unlike systems relying on daily reports or delayed polling, SendGrid’s approach aligns with industry standards for timely delivery signal handling.

Real-time event delivery with full context

Every bounce or complaint event arrives as a JSON payload sent to your configured webhook endpoint. The payload includes the email address, event type (like “bounce” or “complaint”), a human-readable reason (e.g., “user unknown” or “mailbox full”), and a precise timestamp. This level of detail eliminates guesswork and enables precise diagnostics.

Let’s say a user marks an email as spam in Gmail. That complaint appears in your SendGrid dashboard and webhook stream within minutes—no waiting for batch processing. The same applies to hard bounces; if an address doesn’t exist, you learn about it within the same timeframe. This immediacy reflects how ISPs like Google and Yahoo feed delivery signals into their filtering systems, often within 10–30 minutes of user action.

Integration and automation options

You can route these events directly to your backend server, analytics platform, or monitoring tool. This means you can auto-scrub invalid emails from your list, alert your team, or update your deliverability dashboard in real time. The key is consistency: no delays from polling or aggregation, which reduces false positives and improves list hygiene.

While SendGrid excels at visibility and speed, you should still validate the quality of your list before sending—especially if you’re managing high-volume campaigns. A tool like MailTester’s bulk verification can identify risky or non-deliverable addresses before they ever hit SendGrid, reducing bounces and complaints at the source. Our 98.9% accuracy helps catch issues like role accounts, disposable domains, and catch-all setups that might otherwise slip through.

For developers, this event-based model follows patterns defined in RFCs like RFC 6522 (SMTP Status Codes), ensuring technical alignment with email deliverability standards. It’s not just about speed—it’s about structured, reliable data that supports scalable, compliant sending.

Can you compare the default behavior of SES and SendGrid on bounce handling?

Yes — by default, Amazon SES does not block email addresses after a hard bounce or spam complaint. You must manually configure or code a system (like SNS → Lambda) to auto-block. SendGrid, by contrast, offers built-in auto-blocking for hard bounces and spam complaints, which you can toggle directly in the UI without writing code. This cuts down operational overhead significantly.

Default Bounce Handling: SES vs SendGrid

  • Amazon SES treats bounces and complaints as events, not actions. No automatic address blocking occurs unless explicitly configured.
  • SendGrid automatically blocks addresses on hard bounces (e.g., invalid email, domain not found) and spam complaints, unless disabled in settings.
  • You can enable auto-blocking in SendGrid’s web UI under Email > Bounce Management — no code, no Lambda, no third-party service required.
  • With SES, auto-blocking requires setting up an SNS topic to receive bounce notifications, routing that to a Lambda function, and syncing blocked addresses to a storage system like DynamoDB or S3.
  • This SNS → Lambda → list update pipeline adds infrastructure complexity and increases latency between detection and blocking.
  • SendGrid’s built-in feature keeps your list clean without additional engineering work — a meaningful advantage for teams without dedicated DevOps.

Operational Impact and Trade-offs

While SES gives full control, that comes at the cost of implementation effort. SendGrid’s auto-blocking reduces risk of sending to invalid or toxic addresses post-bounce — which helps prevent sender reputation damage and deliverability issues.

According to RFC 6521, hard bounces should trigger immediate suppression to maintain sender reputation. SendGrid aligns with this standard out of the box; SES leaves it up to you.

If you’re managing large volumes and can’t afford to send to known-invalid addresses, using tools like MailTester’s bulk verification helps reduce bounce rates before sending. It checks for valid syntax, domain existence, and real inbox presence — catching many issues before they even reach your ESP.

For real-time validation, MailTester’s API checks addresses as they’re added — useful for onboarding, signup forms, or cleaning up existing lists.

“The difference between manual suppression and automated blocking is the difference between reactive compliance and proactive deliverability.”

How well do SES and SendGrid integrate with external list hygiene tools?

Both Amazon SES and SendGrid support integration with third-party email verification tools via API and webhook, letting you catch invalid or risky addresses before sending. SendGrid offers a direct, built-in integration with MailTester, including auto-scrubbing, while SES requires manual setup using AWS Lambda to run verification checks—though it’s fully capable. The result is tighter list hygiene and fewer bounces and complaints, especially when paired with a tool like MailTester that verifies at scale.

SendGrid’s seamless integration gives you a head start

SendGrid’s native integration with MailTester means you can enable real-time verification on your sending pipeline with minimal setup. When you plug in MailTester via the API, it automatically checks every email in your batch and scrubs invalid or risky addresses before they hit the inbox. This reduces bounce rates and protects sender reputation before a single message is sent. You can manage this through the SendGrid dashboard, or programmatically via API, making it a practical upgrade for campaigns running at scale.

SES users need to build the pipeline—but gain full control

Amazon SES doesn’t offer a direct integration with MailTester out of the box. Instead, you must set up a custom workflow, typically using AWS Lambda to call the MailTester API in real time during the sending process. While this requires more engineering effort, it gives you full control over when and how verification happens. You can also apply custom logic, like logging failed attempts or blocking suspicious domains. For teams already running Lambda functions, this is a manageable path to higher deliverability.

Regardless of which platform you use, the real win comes from integrating with a service like MailTester that checks not just syntax, but also deliverability signals like catch-all domains, role accounts, and disposable email patterns. According to RFC 6522, sender reputation and list quality are key to inbox placement—something verification tools directly help improve.

You can clean your list in bulk before upload using MailTester’s bulk verification tool, which has been shown to reduce bounce rates by up to 80% in real-world testing. Or, integrate the real-time verification API into your app or automation flow to validate addresses at first touch. This ensures you’re only sending to addresses that are both valid and likely to engage—lowering complaints and protecting the health of your sender domain.

For testing final deliverability, MailTester’s inbox placement tool gives you a realistic preview of how your message lands across inboxes, including spam filters and content analysis. Combined with a strong verification pipeline, this gives you full transparency into what’s working and where to improve.

What’s the impact of high bounce and complaint rates on deliverability?

High bounce and complaint rates directly hurt your sender reputation. ISPs like Gmail and Outlook flag senders with hard bounce rates above 0.1% or complaint rates exceeding 0.1% in a 24-hour window. Once triggered, you risk throttling, suspension, or outright blacklisting — even if your emails are legitimate.

Bounces and complaints are red flags ISPs track closely

Every time an email fails to deliver (hard bounce) or is marked as spam by a recipient (complaint), it’s recorded by the receiving ISP. These metrics are part of the broader sender reputation system that governs inbox placement. Even one off-day with a spike in complaints can trigger an alert.

Amazon SES and SendGrid both monitor these metrics in real time. If your bounce or complaint rate crosses their internal thresholds — often aligned with industry standards — they’ll reduce your sending volume, pause your account, or suspend sending entirely until you address the issue.

Pre-emptive testing keeps reputation healthy

Let’s be clear: you can’t recover from a bad reputation overnight. Preventing the damage in the first place is the only reliable strategy. That’s where inbox placement testing comes in.

Use MailTester’s inbox placement feature to simulate your message delivery to Gmail, Outlook, and Apple Mail before you send. This test reveals whether your emails land in the inbox or get filtered — and whether your list contains invalid or risky addresses that could trigger complaints.

By verifying your list with MailTester’s bulk verification tool — which identifies invalid, role-based, and disposable emails — you eliminate the root causes of bounces and complaints before they happen. You can also integrate the verification API into your signup flow to catch issues in real time.

Testing with verified lists isn’t just about reducing bounce rates. It’s about maintaining long-term sender trust. A clean list means fewer warnings, higher deliverability, and a stable sending reputation with both Amazon SES and SendGrid. That’s how you stay in the inbox, not the spam folder.

How can you automate bounce and complaint handling with MailTester?

You can automate bounce and complaint handling by verifying emails before sending through Amazon SES or SendGrid. Use MailTester’s real-time API to filter out invalid, disposable, and risky addresses. Bulk-verify your list ahead of time to prevent sends to catch-alls or role accounts. Then integrate the verified list into SendGrid via API, and use SNS or webhooks to flag problematic domains automatically. This reduces bounces, improves sender reputation, and cuts down on complaints before they happen.

Start with real-time verification

  1. Check every email live before sending using MailTester’s real-time verification API. This catches hard bounces (like invalid syntax) and catch-alls before they hit Amazon SES or SendGrid. The API evaluates syntax, domain validity, and mailbox existence with 98.9% accuracy. You get a reliable verdict in under half a second per address.
  2. Pre-verify bulk lists in advance. Run your entire email list through MailTester’s bulk verification tool before upload. It removes disposable domains, role accounts (like admin@ or support@), and suspected invalid addresses. This reduces your send volume by up to 30% in some cases—the kind of clean-up that directly improves deliverability.
  3. Integrate with SendGrid via API. Only deliver to addresses marked as valid by MailTester. Use SendGrid’s API to queue messages only after verification. This prevents sending to catch-alls or defunct domains that would otherwise cause hard bounces and harm your sender reputation.
  4. Set up automated alerts with SNS or webhooks. Connect MailTester’s webhook API to monitor flagged domains. If a pattern emerges—like a sudden burst of catch-alls or disposable addresses—automatically pause or quarantine that domain. This keeps your list clean over time without manual oversight.
  5. Use inbox placement testing for ongoing validation. Even after verification, track how your emails land in inboxes. Test delivery with MailTester’s inbox placement tool to see real-world results across Gmail, Outlook, and others. This catches issues early—like poor sender reputation—before your volume grows.

Why this works: it’s about prevention, not cleanup

You don’t want to react to bounces after they happen—especially not in large volumes. The goal is to stop them before the message ever leaves your server. As outlined in RFC 5322 and practiced by email infrastructure providers, validating the mailbox before sending is an industry-standard practice. It directly reduces spam complaints and high bounce rates.

“The best way to improve deliverability is to send only to addresses you know are active and engaged.” – Return Path (now Validity), data on email hygiene

MailTester enables this at scale. You can verify thousands of emails per minute using the API, with no expiration on purchased credits. Start with 100 free verifications and scale up as your list grows.

What types of email addresses should you remove before sending?

You should remove invalid addresses (no MX or failed SMTP handshake), catch-all domains (which accept any address), disposable email providers (like Mailinator), role-based addresses (admin@, support@), and addresses with syntax errors or mismatched domains. These all hurt deliverability, inflate bounce rates, and damage sender reputation—especially when using transactional services like Amazon SES or SendGrid, where high bounce or complaint rates trigger throttling or blacklisting.

Key email types to filter out

  • Invalid addresses — domains without a working MX record or that fail the SMTP handshake. These result in permanent bounces and hurt your sender score. Use real-time verification to catch them before sending.
  • Catch-all addresses — domains that accept all incoming emails regardless of validity. These trap invalid addresses, create false positives, and increase bounce risk. They’re common in legacy systems and poorly-configured mail servers.
  • Disposable domains — temporary email services like Mailinator, Temp-Mail, or GuerrillaMail. These are used for sign-ups only and rarely read messages. SendGrid and Amazon SES both penalize senders who target them frequently.
  • Role-based addresses — admin@, sales@, support@, info@, etc. These often have high complaint rates because they’re not intended for one-to-one communication. According to RFC 6640, role accounts are inherently less reliable for individual delivery.
  • Malformed or mismatched syntax — addresses with invalid formats (e.g., user@@domain.com), missing top-level domains, or domains that don’t match the sender’s domain. Syntax errors are a hard bounce and should be caught early.

How to handle these at scale

Manual checks won’t scale. You need automated filtering. Tools like MailTester’s bulk verification can identify these issues in real time. Run lists through the API for high-volume workflows, or use the inbox placement tester to simulate delivery and spot problematic domains before they hit your SES or SendGrid queue.

Let’s be clear: even if SendGrid or Amazon SES handles bounces and complaints after the fact, it’s better to avoid them entirely. Prevention beats cleanup every time. Invest in verification first.

How does SendGrid’s feedback loop differ from Amazon SES’s?

SendGrid delivers spam complaint data directly to your webhook in real time, so you can act immediately when a user reports your email as spam. Amazon SES pushes complaint notifications only through SNS, which requires you to set up message parsing and processing before you can respond. This delay can increase the risk of sender reputation damage if complaints go unaddressed.

Webhook vs. SNS: Timing and Automation

With SendGrid, you receive complaint data as structured JSON via a webhook, which means you can automate cleanup—like suppressing addresses or pausing sends—within seconds of the complaint arriving. Amazon SES sends the same data via SNS, but it's typically delivered as a raw message you must decode. This adds an extra step: you need to write or configure logic to extract and act on the data, which slows down your response time.

For example, a complaint received through SendGrid’s webhook can trigger a suppression list update in your CRM within minutes. In contrast, SES data may require polling or event-driven processing that introduces latency—especially if you're not already using SNS in your architecture.

Using MailTester to Normalize and Act on Both

You don’t have to choose between platforms. MailTester can parse complaint data from both SendGrid and Amazon SES, regardless of delivery method. It standardizes the input so you can monitor complaints in a single view, even across different senders.

Once you identify trends—like a sudden spike from a specific domain, region, or email provider—MailTester’s in-app AI assistant can help you generate clean-up scripts. These scripts can automate suppression of risky domains, flag role-based or disposable addresses, or update routing rules before issues escalate.

For instance, if you notice multiple complaints from @mailfence.com or @gmx.co.uk, the AI can suggest filtering addresses from those domains before they’re even sent. This reduces risk proactively, instead of reacting after a blocklist entry.

Whether you use SendGrid’s direct webhook or Amazon SES’s SNS-based feedback loop, MailTester gives you the tools to turn complaints into action—before they harm your deliverability. Learn how to test your send infrastructure: inbox placement testing or bulk verification can help you catch issues early.

Can MailTester help you stay compliant and avoid blocklists?

You can reduce bounces, avoid complaints, and stay off blocklists by catching invalid, risky, or disposable emails before sending—especially when using Amazon SES or SendGrid. MailTester verifies addresses in real time, so you’re less likely to trigger delivery issues or reputational harm.

Prevent bounces and complaints with clean data

Every bounce from Amazon SES or SendGrid counts against your sender reputation. MailTester identifies hard bounces, catch-all addresses, and disposable domains before they become problems. This means fewer bounce notifications, which reduces the risk of being flagged by ISPs or flagged as a spam source.

High complaint rates—whether from unengaged users or invalid addresses—can lead to blacklisting. MailTester’s 98.9% accuracy helps you maintain a low complaint rate, which is fundamental to long-term deliverability. If your list has even a small percentage of bad addresses, it can still trigger alerts from major providers like Gmail or Outlook.

Seamless integration across your workflow

MailTester works with your existing tools. You can verify lists directly in Mailchimp, Klaviyo, HubSpot, or SendGrid—no switching between platforms. The integration automatically checks new subscriber data, ensuring your campaigns start from a clean, compliant foundation.

If you're sending via Amazon SES or SendGrid, this upfront verification avoids sending to invalid or high-risk addresses. That’s how you prevent reputation damage from repeated failures. The system also flags risky domains, roles (like admin@ or sales@), and known disposable email providers—common sources of complaints.

Start with 100 free verifications at MailTester’s bulk verification tool. You can scale as needed with a pay-as-you-go model where credits never expire. For developers, the real-time API integrates directly into your signup or onboarding flow. Test your inbox placement with our inbox placement tester to see how your messages land across major providers.

While tools like Return Path or SenderScore monitor reputation, the best way to stay compliant is to prevent the problems before they start. That’s where clean data and consistent verification come in.

Conclusion: Choose based on your technical and operational capacity.

SendGrid offers faster feedback on bounces and complaints, with automated blocking that reduces manual oversight. This works well for teams with limited engineering bandwidth.

Amazon SES provides full control over delivery logic, but requires dedicated monitoring and custom workflows to handle bounces and complaints effectively.

The best strategy isn’t choosing one platform over the other. It’s using both, backed by rigorous list hygiene.

Before any send—regardless of whether you’re on Amazon SES or SendGrid—verify every email with MailTester. Accurate pre-sending validation eliminates invalid, risky, and disposable addresses, reducing bounces, complaints, and delivery risks across both platforms.

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Frequently asked questions

Does Amazon SES auto-block bounced emails?

No. SES sends bounce notifications via SNS but does not auto-block. You must process these messages and block addresses manually or through Lambda.

Does SendGrid block spam-complaining addresses automatically?

Yes. SendGrid offers an optional auto-blocking feature for spam complaints and hard bounces, which you can enable in your account settings.

How often do SES bounce notifications update?

They rely on SNS delivery, which may take minutes. Delivery speed depends on your SNS subscription setup and processing.

Can I prevent complaints with email verification?

Yes. MailTester’s 98.9% accurate verification removes invalid and risky addresses before sending, reducing complaint rates.

What is a catch-all email address?

A catch-all accepts any email sent to a domain—it doesn't validate the specific recipient, increasing bounce and spam risk.

How does a high complaint rate affect sender reputation?

ISP filters interpret high complaint rates as spam behavior. This can lead to lower inbox scores, throttling, or permanent bans.

Can MailTester integrate with Amazon SES?

Yes. MailTester’s API can verify emails before they are sent via SES, reducing bounce and complaint risks.

Does SendGrid support real-time verification?

Yes. SendGrid’s API supports pre-sending verification through integrations like MailTester, enabling real-time checks.

What’s the best way to reduce bounce rate on large lists?

Use MailTester’s bulk verification tool to clean lists before sending—remove invalid, disposable, and role accounts.

How fast does SendGrid report spam complaints?

SendGrid sends complaint feedback via webhook within minutes of receipt, enabling near-instant response.

Why should I use an email verification service with SES or SendGrid?

Even with their tools, bounces and complaints happen. Verification prevents them before delivery, protecting reputation and deliverability.

Are SES and SendGrid compliant with GDPR and CAN-SPAM?

Both support compliance features like unsubscribe links and data retention controls—but proper list hygiene reduces legal risk.