Summary
When AWS SES emails appear to be stuck in 'Send' status, it typically means they have been accepted by SES but are experiencing delays or non-delivery due to various underlying issues beyond the initial acceptance point. These can include transient network errors, account-level suppression, exceeding sending quotas, a poor sender reputation, misconfigured email authentication (SPF, DKIM, DMARC), or problems on the recipient's mail server. Effective investigation relies on leveraging SES's monitoring tools and notification systems to gain detailed insights into the final disposition of each email.
Key findings
- Acceptance vs. Delivery: An email in 'Send' status indicates acceptance by SES and queuing for delivery, but not immediate or guaranteed recipient delivery, which can be influenced by external factors and asynchronous processes.
- Suppression Mechanisms: Emails can appear 'stuck' if they are suppressed, either on your account's suppression list due to previous hard bounces or on a global ESP blacklist, preventing actual delivery.
- Sending Quota Limitations: Exceeding your Amazon SES sending limits will cause SES to throttle or defer your emails by queuing them internally, leading to significant delays.
- Sender Reputation Issues: High bounce and complaint rates severely harm your sender reputation, potentially leading to SES throttling your sending or recipient mail servers delaying and rejecting your emails.
- Authentication Configuration: Misconfigured SPF, DKIM, or DMARC records can result in recipient mail servers distrusting your emails, leading to greylisting, rejections, or delays.
- Recipient Server Challenges: Issues on the recipient's mail server, such as overload, temporary rejections (greylisting), or aggressive spam filters, can delay or block delivery even if SES accepted the email.
- Content-Based Filtering: Emails with suspicious or spammy content can be delayed or blocked by recipient spam filters, making them appear 'stuck' despite SES processing.
- Sandbox Mode Restrictions: New SES accounts in sandbox mode are restricted to sending only to verified email addresses or domains; attempts to send to unverified recipients will not be delivered.
Key considerations
- Configure SNS Notifications: Setting up Amazon SNS notifications for bounces, complaints, and deliveries is crucial for real-time, detailed feedback on email disposition, allowing you to understand precisely why emails might be delayed or not delivered.
- Monitor SES Metrics and Quotas: Regularly review your CloudWatch metrics in the SES console, including sending volume, bounce rates, and complaint rates. Also, check your current sending quotas and usage, requesting limit increases if you anticipate sending large volumes.
- Practice Proactive List Hygiene: Actively remove hard-bounced and invalid email addresses from your mailing lists to prevent future sends to suppressed recipients and to maintain a strong sender reputation.
- Verify DNS Records and Authentication: Double-check your domain's DNS settings to ensure SPF, DKIM, and DMARC records are correctly published and your domain status in SES is 'verified,' as misconfigurations can lead to rejections.
- Review Email Content: Analyze your email content for elements that could trigger spam filters, such as excessive capitalization, suspicious links, or certain keywords, ensuring your emails are well-formatted and trustworthy.
- Understand Sandbox Mode: If your SES account is in sandbox mode, ensure all recipients are verified, or request production access to send to unverified email addresses.
- Analyze DeliveryDelay Events: Look for specific DeliveryDelay events in your SES logs or notifications, as these can provide more detailed information about why delivery is being deferred.
What email marketers say
10 marketer opinions
AWS SES emails appearing 'stuck' in a 'Send' status means they have been accepted and queued by SES, but their final delivery is pending or experiencing issues. This status often masks underlying problems such as transient network errors, exceeding sending quotas, recipient server complications like greylisting or overload, or a tarnished sender reputation. Crucially, a lack of detailed delivery event notifications means senders often lack the visibility needed to diagnose these delays effectively. Investigating requires proactive monitoring of SES metrics and the configuration of comprehensive event notifications.
Key opinions
- Asynchronous Delivery: An email in 'Send' status signifies SES acceptance and queuing, but actual delivery is an asynchronous process, subject to various external and internal factors.
- Transient Delivery Issues: Delays can stem from temporary network errors or deferred delivery attempts by SES or recipient servers, often indicated by specific DeliveryDelay events.
- Suppression List Impact: Emails may remain in 'Send' if they are suppressed due to previous hard bounces, either on your account-specific list or a broader global blacklist maintained by some ESPs.
- Quota-Related Throttling: Exceeding SES sending quotas causes emails to be internally queued and throttled by SES to protect its reputation, leading to significant delays.
- Authentication & DNS Flaws: Misconfigured or missing SPF, DKIM, and DMARC records critically undermine email trust, often causing recipient servers to greylist, delay, or reject messages.
- Recipient Server Bottlenecks: Delays or failures can originate from the recipient's mail server, including overload, temporary rejections like greylisting, or aggressive spam filtering.
- Sender Reputation Damage: High bounce or complaint rates severely degrade your sender reputation, prompting SES to throttle your account and increasing the likelihood of recipient rejections or delays.
- Content-Triggered Filtering: Suspicious or spammy email content can activate recipient spam filters, leading to the email being delayed or blocked in transit.
- Visibility Gap: Without explicit configuration of event notifications, senders lack crucial visibility into the precise delivery status, leaving them guessing why emails appear 'stuck'.
Key considerations
- Essential SNS Configuration: Implement Amazon SNS notifications for bounces, complaints, and deliveries to gain real-time, granular insights into the ultimate disposition of each email, revealing exact delivery issues.
- Quota and Metric Monitoring: Consistently monitor your SES sending quotas, bounce rates, and complaint rates within the SES console, and plan for quota increases as needed.
- Rigorously Maintain List Hygiene: Regularly clean your mailing lists by promptly removing hard-bounced addresses and invalid contacts to improve deliverability and maintain a healthy sender reputation.
- Thorough DNS Validation: Verify that your domain's SPF, DKIM, and DMARC records are correctly published and that your domain is verified in SES, as proper authentication is critical for trust.
- Proactive Content Optimization: Review email content for common spam triggers, ensuring messages are well-formatted, relevant, and free of suspicious elements that could lead to content-based filtering.
- Strategic Account Warm-up: For new accounts or large campaigns, adopt a gradual warm-up strategy to build sender reputation and avoid triggering SES throttling mechanisms.
- Analyze Delivery Delay Events: Investigate specific DeliveryDelay events, if available through your SES logs or notifications, for detailed reasons behind deferred deliveries.
- Address Complaint Feedback: Analyze reasons for complaints received via SNS and adjust sending practices, content, or list segmentation accordingly to reduce future complaints.
- Evaluate Suppression Strategy: Consider moving to account-level suppression for greater control over bounced addresses, ensuring robust internal bounce handling rules are in place.
Marketer view
Marketer from Email Geeks explains that a Send event typically means an email has been accepted by SES and is queued for delivery, potentially due to transient errors or deferred delivery. He suggests checking for DeliveryDelay events for more details.
27 Aug 2021 - Email Geeks
Marketer view
Marketer from Email Geeks shares that some ESPs use a common global blacklist, where hardbounced addresses are suppressed from future sends for all customers, and their status might appear "shadowy," similar to the Send status.
14 May 2025 - Email Geeks
What the experts say
3 expert opinions
When emails sent via AWS SES remain in a 'Send' status, it signals that they were accepted by SES but are experiencing delays or non-delivery further downstream. Common culprits include recipient server issues, ISP throttling, content-based filtering, exceeding rate limits, or a compromised sender reputation. Investigating these delays involves meticulously reviewing SES delivery logs and bounce notifications, even if delayed, to pinpoint specific error messages or indications of throttling.
Key opinions
- Suppression List Impact: Emails may appear 'stuck' if they are on a suppression list, preventing actual delivery despite being accepted by SES initially.
- Recipient-Side Delays: Issues on the recipient's mail server, including temporary problems or overload, can significantly delay or completely block email delivery.
- ISP Throttling & Rate Limits: Internet Service Provider (ISP) throttling or exceeding your AWS SES sending rate limits can cause emails to be delayed, appearing to be 'stuck' in the send queue.
- Content-Based Rejection: Suspicious or problematic email content is often a reason for recipient servers to filter, delay, or outright reject messages.
- Sender Reputation Impact: A poor sender reputation, affecting either your IP address or domain, frequently leads to recipient servers filtering or delaying your emails.
- Delayed Bounce Feedback: Bounce notifications, while crucial for diagnosing delivery issues, may not be immediate, requiring patience and thorough log review to identify the root cause.
Key considerations
- Thorough Log Analysis: Meticulously review your AWS SES delivery logs and event data for specific error codes or detailed reasons for non-delivery or delays, as these logs are crucial for diagnosis.
- Monitor Bounce & Complaint Notifications: Actively monitor Amazon SNS notifications for bounces and complaints, even if they are delayed, as these provide critical diagnostic information about delivery failures and filtering.
- Address Sender Reputation: Regularly assess and work to improve your sender reputation, which can be negatively impacted by high bounce and complaint rates, leading to recipient server filtering.
- Adhere to Rate Limits: Be aware of and operate within your AWS SES sending rate limits to avoid internal throttling and queuing of your emails.
- Optimize Email Content: Review your email content for elements that might trigger spam filters, ensuring messages are clear, relevant, and adhere to best practices to avoid content-based rejections.
- Investigate Recipient Server Issues: Recognize that recipient server problems, such as overload or temporary rejections, are common causes of delays, and look for indications of such issues in your delivery logs.
Expert view
Expert from Email Geeks suggests that emails remaining in Send status might be due to suppression.
14 Jan 2025 - Email Geeks
Expert view
Expert from Spam Resource explains that emails, including those from AWS SES that appear 'stuck in Send' status, often face delays or disappearance due to issues such as recipient server problems, ISP throttling, or content-based filtering. Investigation involves monitoring for bounce notifications, even delayed ones, and meticulously reviewing sending logs for any error messages or indications of throttling from the receiving end. This helps pinpoint why an email hasn't reached its final destination, despite being accepted for sending by SES.
13 Dec 2021 - Spam Resource
What the documentation says
5 technical articles
Emails sent through AWS SES that remain in a 'Send' status are often encountering issues beyond initial acceptance by the service. This can happen due to surpassing your account's sending quotas, triggering your account-level suppression list for previously bounced addresses, or operating within the restrictions of a new account's sandbox mode. Investigating these delays primarily relies on leveraging SES's built-in monitoring tools, such as CloudWatch metrics and especially Amazon SNS notifications, to gain granular insight into delivery outcomes, bounces, and complaints.
Key findings
- Acceptance vs. Delivery: An email in 'Send' status indicates that Amazon SES has accepted it for processing, but this does not guarantee immediate or successful delivery to the recipient. The actual delivery process is asynchronous and subject to external factors.
- Quota-Based Throttling: Exceeding your Amazon SES sending limits can cause SES to throttle or defer your emails, queuing them internally and making them appear 'stuck' for extended periods before eventual delivery or failure.
- Account Suppression Impact: Emails sent to addresses on your account's suppression list, typically due to previous hard bounces, will be accepted by SES but not delivered. They will appear 'sent' from your application's perspective.
- Sandbox Mode Restrictions: New SES accounts operate in sandbox mode, limiting sends to only verified email addresses or domains. Attempts to send to unverified recipients will be accepted by SES but will not be delivered, leading to perceived stuck emails.
- Real-Time Visibility Necessity: Without proper configuration of Amazon SNS notifications and monitoring of CloudWatch metrics, it's challenging to ascertain the precise reason why emails might be delayed or appear 'stuck' in the Send status.
Key considerations
- Configure SNS Notifications: Set up Amazon SNS notifications for bounces, complaints, and deliveries. This is vital for obtaining real-time, detailed insights into the final disposition of your emails, which helps pinpoint the exact reasons for non-delivery or delays.
- Monitor Quotas and Usage: Regularly check your current sending quotas and usage within the SES console. If your sending volume is high or increasing, consider requesting a limit increase to avoid throttling or deferral of your emails.
- Manage Suppression List: Proactively review your SES account-level suppression list. Implement robust bounce handling to ensure invalid email addresses are removed from your mailing lists, preventing future sends to suppressed recipients.
- Address Sandbox Mode: Confirm whether your SES account is still in sandbox mode. If you need to send to unverified addresses, you must request production access, or ensure all intended recipients are verified within SES while in sandbox.
- Analyze CloudWatch Metrics: Utilize CloudWatch metrics in the SES console to gain valuable insight into your overall sending activity, including send rates, bounce rates, and complaint rates, which are crucial for identifying potential issues.
Technical article
Documentation from AWS Documentation explains that when SES accepts an email, it moves to the 'Sending' state, which signifies acceptance for processing but not necessarily immediate delivery to the recipient. Actual delivery can be asynchronous and influenced by external factors. To investigate, it's essential to monitor delivery metrics in the SES console and configure SNS notifications for bounces, complaints, and deliveries to gain detailed insights into the final status of emails.
5 Jul 2023 - AWS Documentation
Technical article
Documentation from AWS Documentation shares that CloudWatch metrics provide valuable insight into your SES sending activity, including the number of sends, bounces, and complaints. For immediate, real-time notifications about delivery, bounces, and complaints, configuring Amazon SNS notifications is crucial. This setup helps to identify precisely why emails might appear 'stuck' by providing specific reasons for delivery failures or issues.
23 Mar 2025 - AWS Documentation
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