When you're relying on a cloud provider like Amazon Web Services (AWS) for your email sending infrastructure, it's natural to wonder about potential deliverability challenges. While Amazon Simple Email Service (SES) is a highly scalable and cost-effective service, it's not immune to issues that can impact your email deliverability. From service outages to specific configuration errors or even broader internet problems, various factors can lead to sending difficulties.
My experience shows that most email sending issues with AWS aren't inherent flaws in the service itself, but rather stem from misconfigurations or reputation management challenges. Understanding how AWS handles email, what its limitations are, and how to properly troubleshoot will help you maintain strong inbox placement rates.
Understanding AWS SES and common limitations
Amazon SES is designed for bulk email sending, covering everything from transactional emails to marketing campaigns. It offers robust features for email authentication, such as SPF and DKIM, to help ensure your emails are legitimate. However, when you first start using SES, your account is typically placed in a sandbox environment. This means you can only send emails to verified email addresses or domains, and you have lower sending limits. To send to any address and increase your volume, you must request production access.
Another common limitation comes into play if you're trying to send email directly from an AWS EC2 instance without using SES. By default, AWS blocks outbound traffic on port 25 to prevent spam and abuse. If you require sending email through port 25, you need to submit a specific request to have this restriction removed for your EC2 instance. This is a crucial step often overlooked by new users, leading to immediate sending failures.
Furthermore, every sender identity (email address or domain) you use with SES must be verified to prove ownership and prevent unauthorized sending. If an email fails to send with an "Email address is not verified" error, it's a clear indication that this verification step was missed or is incomplete. Verifying your domains ensures that AWS can associate your sending activity with your legitimate identity.
Sandbox mode vs. production
Sandbox limits: You can only send to and from verified email addresses and domains.
Sending quota: Daily sending limits and maximum send rates are significantly lower.
Even with correct configuration, your emails might not reach the inbox. A primary reason is your sender reputation. AWS, like other email service providers (ESPs), closely monitors bounce rates, complaint rates, and other engagement metrics. High numbers in these areas signal poor sending practices, which can lead to AWS automatically pausing your sending or, in severe cases, terminating your account. It's a strict but necessary measure to maintain the health of their email infrastructure.
Another frequent culprit is incorrect or incomplete email authentication. While SES helps by providing the tools, it's up to you to implement SPF, DKIM, and DMARC correctly. If these records are missing or misconfigured, receiving email servers (especially those run by Gmail and Outlook) are likely to flag your emails as spam or reject them outright. This is critical for preventing your emails from landing in spam folders.
Finally, even if your setup is perfect, recipient-side issues can cause delivery problems. An email might be delayed if the recipient's inbox is full, or it might be rejected if the recipient's ISP has temporarily blocked your IP or domain. Sometimes, a receiving mail server might experience a transient issue, leading to deferrals rather than outright rejections. These are often temporary and resolve themselves, but they can still cause frustrating delays.
Common problems
Reputation issues: High bounce rates, spam complaints, or sending to bad lists.
Authentication failures: Misconfigured SPF, DKIM, or DMARC records lead to rejections.
Account restrictions: Still in sandbox mode or port 25 blocked on EC2 instances.
Email rejections: Emails are immediately bounced back to the sender.
Spam folder placement: Legitimate emails end up in the junk folder.
Delivery delays: Emails take an unusually long time to arrive.
Account suspension: AWS may pause or suspend your sending capabilities.
Troubleshooting steps for AWS email problems
When you encounter email sending issues with AWS, your first stop should always be the AWS Service Health Dashboard. This provides real-time information on the status of all AWS services, including SES. If there's a widespread outage affecting SES in your region (like US-East-1, as we've seen in the past), it will be clearly reported there. Knowing it's a systemic issue can save you hours of individual troubleshooting.
If the dashboard shows no issues, dive into your Amazon SES metrics. This includes tracking your bounce rate, complaint rate, and successful deliveries. A sudden spike in bounces or complaints is a critical warning sign that your sender reputation is taking a hit. AWS also provides detailed email sending error messages that can point you directly to the root cause, such as unverified sender identities or throttling due to high rates.
For specific delivery failures, check your Amazon SES logs and any bounce or complaint notifications you receive. These logs often contain detailed information about why an email was not delivered or why it was placed on a blocklist (blacklist). Additionally, ensure your SPF, DKIM, and DMARC DNS records are correctly configured and aligned. A common issue is a DKIM alignment failure, which can lead to emails being marked as spam. Using a tool to check your DMARC reports can illuminate these issues.
Review logs: Examine SES sending logs and notifications for specific errors.
Maintaining good email deliverability on AWS
The key to sustained email deliverability with AWS SES lies in proactive management of your sender reputation. This means starting with a clean, opted-in email list and regularly removing inactive or invalid addresses. Neglecting list hygiene is a sure-fire way to increase your bounce and complaint rates, which will negatively impact your standing with AWS and internet service providers (ISPs).
Beyond list quality, pay close attention to your email content and sending patterns. Avoid spammy keywords, excessive images, or suspicious links that might trigger filters. For new sending IPs or domains, a gradual warmup process is essential. Sending a low volume initially and slowly increasing it allows ISPs to build a positive reputation for your sending. This helps avoid sudden spikes that can be mistaken for spamming activity. It's similar to warming up new IP addresses.
Lastly, integrate and monitor feedback loops from SES. These provide real-time notifications about bounces and complaints, allowing you to quickly remove problematic addresses from your lists. Proactive monitoring and adherence to best practices are crucial for long-term email deliverability success on AWS. Regularly checking your DMARC reports also helps identify any authentication issues before they severely impact your reputation.
Views from the trenches
Best practices
Maintain a healthy email list by regularly cleaning it of invalid or inactive addresses.
Implement strong email authentication, including SPF, DKIM, and DMARC, and monitor their alignment.
Gradually increase your sending volume for new IPs or domains to build a positive sender reputation.
Utilize Amazon SES feedback loops to immediately remove bouncing addresses and complaint senders.
Common pitfalls
Neglecting to apply for production access, keeping your account in the low-limit sandbox mode.
Failing to verify sender identities, leading to immediate rejection of emails.
Ignoring high bounce or complaint rates, which can result in AWS account suspension.
Trying to send emails directly from EC2 instances without requesting port 25 unblocking.
Expert tips
Monitor the AWS Service Health Dashboard for regional outages affecting SES before troubleshooting your setup.
Regularly review your Amazon SES sending metrics for early signs of deliverability issues.
Analyze DMARC reports to detect and fix authentication problems impacting inbox placement.
Keep your email content relevant and engaging to reduce complaint rates and improve recipient engagement.
Marketer view
Marketer from Email Geeks says a general AWS outage can significantly impact email sending, indicating it's not always an SES-specific issue.
2021-12-07 - Email Geeks
Marketer view
Marketer from Email Geeks says that AWS experienced some problems, affecting various services beyond just email.
2021-12-07 - Email Geeks
Navigating email delivery with AWS
While AWS SES is a powerful and reliable platform for sending emails, it's clear that email sending issues can and do arise. These problems often stem from common pitfalls like being in sandbox mode, incorrect authentication, or poor sender reputation. Service outages, though rare, can also impact sending temporarily, requiring you to monitor AWS's health status.
By understanding the typical causes of these issues and implementing proactive measures for reputation management and proper configuration, you can significantly improve your email deliverability rates. Regularly monitoring your SES metrics and diligently maintaining your sender identity are key to ensuring your emails consistently reach their intended recipients.
Gmail and 
Outlook) are likely to flag your emails as spam or reject them outright. This is critical for preventing your emails from landing in spam folders.
