If you’re running a SaaS platform, e-commerce site, or any kind of online application, transactional emails are the lifeline between your back-end and your users. Password resets, order confirmations, system alerts—they all rely on email delivery systems that are fast, reliable, and scalable. Amazon SES (Simple Email Service) is often a top choice due to its affordability and robust infrastructure. But what happens when SES unexpectedly clamps down and blocks your flow of outbound emails? That’s exactly what happened to me. What followed was a whirlwind of panic, insight, and ultimately, success as I navigated the sandbox restrictions and rebuilt my domain’s reputation score with SES.
TL;DR
Amazon SES blocked my account after a sudden spike in bounce rates triggered a reputation alert. My transactional emails, including order confirmations and password resets, stopped sending—creating user frustration. I had to revert back to sandbox mode, retrace the issue, and fix my domain and email hygiene practices. Eventually, I escaped the sandbox, improved my sender reputation, and restored full production-level email functionality.
My Account Suspension: The Beginning of the Nightmare
It started like any other Monday. I pushed a batch of 50,000 transactional emails queued for the early morning delivery—order receipts, two-factor authentication emails, and account verifications. Minutes later, we began receiving email bounce notifications, followed swiftly by an alarming notice from AWS: our SES account was
The message stated that sending had been disabled due to high bounce rates and potential account compromise. This instantly threw a wrench in our operations. Support tickets poured in, customers weren’t getting password resets, and new account activations stalled. The root problem? A combination of poor recipient email hygiene and a flawed SMTP routing logic after a recent code update.
Understanding the Sandbox Mode
When Amazon SES detects poor sending behavior, one default action is moving your account back into what they call the “sandbox” environment. Here’s what that entails:
- Limited sending capability – Only verified email addresses and domains can receive your messages.
- Test mode for deliverability – SES treats you like a trial user, severely restricting your operational capacity.
- No mass emailing – No campaign-type emails or large-scale transactional messages.
For a business reliant on mass transactional flow, this is near-paralysis. We had to act fast to diagnose the issue and build a path to redemption.
Diagnosis: What Went Wrong
We initiated a deep investigation into our email logs, SES metrics, and the code changes committed over the weekend. Here’s what we uncovered:
- A new SMTP routing layer bug was causing malformed email headers, leading some messages to get classified as spam.
- Temporary misconfiguration in our bounce handling webhooks meant that bounce notifications from invalid addresses went unchecked.
- An acquisition campaign mistakenly routed through our transactional email IP pool further worsened our reputation.
Effectively, we had triggered all the red flags that SES monitors: high bounce rates, sharp jumps in volume, and spam complaint spikes.
Step-by-Step: The Reputation Repair and Escape Sequence
Amazon SES doesn’t offer a “magic button” to restore your account. Instead, it expects systematic remediation and proof of improved email practices. Here’s the exact sequence we followed:
1. Cleaned Our Email Lists
We ran all our user and subscriber databases through a third-party email validation service, removing all:
- Invalid or inactive addresses
- Role-based emails like info@, admin@
- Spam trap suspects
This alone cut down our bounce rate by nearly 50%.
2. Segregated Campaign from Transactional Traffic
Previously, both promotional and transactional emails shared the same SES line. This was rectified by splitting our email flows:
- Promotional emails routed via a separate ESP (Email Service Provider)
- Transactional emails were kept exclusive to Amazon SES
This ensured domain reputation wasn’t being dragged down by marketing activity.
3. Set Up Dedicated IP and Warm-up Protocols
We upgraded from shared to a dedicated IP address. This gave us more control over our sender reputation. Then, we initiated an IP warm-up process—sending emails in gradually increasing volumes over two weeks to build trust organically.
4. Implemented Feedback Loops and DMARC Enforcement
AWS SES supports integration with feedback loops (FBLs) and domain-level authentication protocols like SPF, DKIM, and DMARC. We enforced them all with:
- SPF and DKIM records mapped correctly to our sending domains
- Enforced
p=quarantineDMARC policy - Real-time bounce and complaint monitoring via webhook
5. Communicated with AWS Trust & Safety
After 10 days of remediation, we opened a support case with detailed evidence:
- Overview of the email list cleaning and bounce metrics before/after
- IP isolation steps and warm-up calendar
- Authentication protocols with DNS screenshots
- Plan for ongoing monitoring
They appreciated the transparency and effort, and within 72 hours, our account was re-evaluated and escalated for sandbox removal.
Key Lessons Learned
This experience, while disruptive, was incredibly valuable. Here are some of the golden takeaways:
- Never send unvalidated emails, even transactional ones. Don’t assume your users are keeping their emails updated or valid.
- Segregate SMTP paths between marketing and operational messages. One will hurt the other if abused.
- Monitor real-time metrics for bounce rate, complaint rate, and delivery latency—automate alerts based on thresholds.
- Warm-up dedicated IPs like you would for a new domain. Gradual volume builds trust.
Final Thoughts: It’s Not Just Infrastructure, It’s Reputation
Amazon SES provides incredible performance but demands discipline. Your sender reputation becomes your passport—and if you violate its terms, SES will lock your doors without warning. The recovery process is open, yes, but it’s rigorous and rooted in your willingness to own the issue, fix the problem, and communicate effectively.
If you’re already using SES or planning to onboard, make sure your email list hygiene, sender architecture, and bounce handling protocols are bulletproof from day one. Once you get burned by an SES block, you’ll never want to risk sloppy email practices again.
May your inboxes be clean, your headers be validated, and your domains always on the whitelisted side of AWS!
