Summary
The 'rate limit exceeded' error in email delivery indicates that you have surpassed a sending threshold imposed by the receiving mail server or your ESP. This is commonly triggered by reputation-based throttling, sudden increases in sending volume, or practices that resemble spam. Troubleshooting involves reviewing bounce logs, analyzing sending patterns, improving sending reputation by warming up IPs/domains, implementing proper authentication (SPF, DKIM, DMARC), cleaning email lists, implementing feedback loops, staggering sends, and adhering to the specific sending guidelines of each email platform. Addressing API rate limits may require implementing exponential backoff strategies or reducing maximum connection settings.
Key findings
- Reputation Impact: Rate limits are frequently linked to your sending reputation. Poor reputation results in stricter limits.
- Volume and Speed: Sending too many emails too quickly, especially to individual recipients, can trigger rate limits.
- ESP-Specific Limits: Each ESP (Gmail, Amazon SES, Exchange Online) has its own sending limits to protect from spam and maintain system reliability.
- API Rate Limits: Surpassing API request limits can result in 'rate limit exceeded' errors, especially with transactional emails.
- Bounce Log Insights: Analyzing bounce logs, especially deferrals from Gmail, reveals reasons like 'unusual rate of unsolicited mail' or suspicious IP/domain reputation.
- Delivery Timeout: A 'delivery time expired' bounce means the ESP tried but failed to deliver an email within the allotted time (typically 24-72 hours).
- Connection limits: Can be tripped due to maximum connection settings.
Key considerations
- Monitor Reputation: Regularly monitor your sending reputation to identify deliverability issues early.
- Warm-Up Gradually: Warm up new IPs and domains gradually to establish a positive sending history.
- List Segmentation: Segment your email list to send targeted content to engaged recipients and suppress unengaged ones.
- Authentication: Implement SPF, DKIM, and DMARC authentication to improve email deliverability.
- Exponential Backoff: When using APIs, implement exponential backoff strategies to retry requests with increasing delays to handle rate limits gracefully.
- Implement Feedback Loops: Set up feedback loops to get feedback from mailbox providers
- Optimize Content: Optimize your email content to avoid spam triggers and improve engagement metrics (open rates, click-through rates).
- Reduce Connections: Reduce number of concurrent connections and/or increase burst delay settings when connection pooling.
- Use a Reputable ESP: Using a reputable ESP means they should be handling the authentication and other settings that will lead to better deliverability.
What email marketers say
10 marketer opinions
A 'rate limit exceeded' error in email delivery indicates that you've surpassed a sending threshold, either in volume or speed, set by the receiving mail server or your email service provider (ESP). This is often triggered by reputation-based throttling, sudden spikes in sending volume, or practices that resemble spam. Troubleshooting involves identifying the cause (e.g., via bounce logs), improving sending reputation, and adjusting sending practices to comply with limits.
Key opinions
- Reputation Impact: Rate limits are often linked to your sending reputation. Poor reputation can lead to stricter limits.
- Sending Volume/Speed: Sending too many emails too quickly can trigger rate limits.
- ESP Limits: ESPs have sending limits that, when exceeded, result in 'rate limit exceeded' errors.
- API Limits: Surpassing allocated API request limits can lead to this error.
- Bounce Log Analysis: Analyzing bounce logs (especially Gmail deferrals) reveals reasons, such as 'unusual rate of unsolicited mail' or 'suspicious reputation'.
- Connection limits: Can be tripped due to maximum connection settings.
Key considerations
- Monitor Sending Reputation: Regularly check your sending reputation to identify and address deliverability issues.
- Gradual Volume Increase: Warm up new IPs/domains and gradually increase sending volume to establish a positive sending history.
- List Segmentation/Cleaning: Segment your email list to send targeted content and remove unengaged subscribers to improve engagement metrics.
- Authentication: Implement proper email authentication (SPF, DKIM, DMARC) to verify your identity and improve deliverability.
- Exponential Backoff: When using APIs, implement exponential backoff strategies to retry requests with increasing delays.
- Queuing Systems: Implement queuing systems to throttle the number of emails sent per minute
- Optimize Email Content: Optimize email content to avoid spam triggers and improve engagement.
- Reduce connections: Reduce number of concurrent connections and/or increase burst delay settings when connection pooling.
Marketer view
Email marketer from StackOverflow suggests that if you are encountering rate limits when using PHP mail, you may need to implement a queuing system to throttle the number of emails sent per minute. He also advises checking with your hosting provider for any sending limits they have in place.
29 May 2021 - StackOverflow
Marketer view
Email marketer from Mailjet explains that 'rate limit exceeded' means you've sent too many emails within a specific timeframe. To troubleshoot, they suggest monitoring your sending reputation, gradually increasing sending volume, and ensuring your email list is clean and engaged.
13 Oct 2023 - Mailjet
What the experts say
4 expert opinions
The 'rate limit exceeded' error in email delivery signifies that sending thresholds, set to combat spam, have been surpassed. This often arises from sending too quickly to individuals or exceeding IP/domain reputation limits. Resolution involves examining bounce logs, enhancing sending infrastructure and authentication (SPF, DKIM, DMARC), implementing feedback loops, and maintaining consistent sending volumes to engaged recipients. A 'delivery time expired' bounce indicates unsuccessful email delivery attempts within a 24-72 hour timeframe.
Key opinions
- Sending Speed/Volume: Exceeding rate limits can be caused by sending too quickly to one recipient or exceeding limits based on IP/domain reputation.
- Bounce Log Analysis: Review bounce logs, especially those from Gmail, to understand specific reasons for delivery failures.
- Throttling Indication: Encountering 'rate limit exceeded' often suggests the receiving server is throttling your server to prevent spam.
- Delivery Timeout: A 'delivery time expired' bounce signifies the ESP couldn't deliver the email within the allotted time (24-72 hours).
Key considerations
- Examine Infrastructure: Review sending infrastructure and authentication setup (SPF, DKIM, DMARC) to improve sender reputation.
- Implement Feedback Loops: Set up feedback loops to receive information about spam complaints and adjust sending practices accordingly.
- Consistent Volume: Maintain consistent sending volumes to engaged recipients to build a positive sending reputation.
- Monitor Reputation: Check IP and Domain reputation
Expert view
Expert from Word to the Wise advises to review your sending infrastructure and authentication setup, and that a good first step is to get set up for feedback loops. A lot of rate limiting and blocking from mailbox providers can be avoided when you are getting the feedback. Also maintain consistent volume and send to engaged recipients.
31 Dec 2022 - Word to the Wise
Expert view
Expert from Email Geeks explains that a delivery time expired bounce means the ESP tried to deliver an email for somewhere between 24-72 hours but wasn't successful in the allotted time.
22 May 2024 - Email Geeks
What the documentation says
3 technical articles
Gmail, Amazon SES, and Microsoft Exchange Online all implement sending limits to protect against spam and abuse, and to maintain system reliability and deliverability. A 'rate limit exceeded' error indicates that you have surpassed these limits, which vary based on account type and activity. Addressing the error requires reviewing sending patterns and adhering to the specific guidelines and sending quotas of each platform, and requesting quota increases where appropriate.
Key findings
- Platform-Specific Limits: Each email platform (Gmail, Amazon SES, Exchange Online) enforces its own sending limits.
- Protection Against Abuse: Sending limits are in place to protect users from spam and maintain system reliability.
- Quota-Based Restrictions: 'Rate limit exceeded' errors indicate exceeding your allocated sending quota or rate.
Key considerations
- Review Sending Patterns: Analyze your email sending patterns to identify potential causes for exceeding limits.
- Adhere to Guidelines: Ensure compliance with the specific sending guidelines and policies of each email platform.
- Request Limit Increases: Consider requesting an increase to your sending limits if your legitimate email needs require it.
Technical article
Documentation from Microsoft explains that Exchange Online has sending limits in place to prevent spam and abuse. If you exceed these limits, you may encounter 'rate limit exceeded' errors. Review your sending patterns and ensure you adhere to Microsoft's guidelines.
23 Sep 2023 - Microsoft
Technical article
Documentation from Amazon SES Documentation states that Amazon SES imposes sending limits to protect its reputation and ensure high deliverability rates for all users. 'Rate limit exceeded' errors indicate that you have surpassed your allocated sending quota or rate. You can request an increase to your limits.
3 Aug 2023 - Amazon SES Documentation
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