Email marketing and transactional emails play a crucial role in communication, but what happens when your emails are delayed or sent at a reduced rate? This phenomenon, known as email throttling, occurs when mail servers intentionally slow down the delivery of your messages.

There are several points where your email delivery rate may be throttled - whether by your email service provider, recipient servers, or spam filters. Throttling can impact your email marketing campaigns, delay important notifications, and even affect your sender reputation.

In this article, we’ll explore the common causes of email throttling, how to identify if it’s happening to you, and the best practices to ensure smooth and efficient email delivery. 
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As you may know, Elastic Email is an all-in-one email delivery platform. We offer an SMTP Relay and REST API as well as the User Interface to submit emails. For users that connect and send via the SMTP Relay and REST API, you must also take into consideration the time it takes to submit all of the emails to the Elastic Email Cloud Network. We do limit each user to 20 concurrent connections for both - SMTP and API. This is to ensure that no single user can abuse or dominate the SMTP and API submission servers. We also recommend setting any connection timeout to at least 30 seconds.

Have you ever encountered a warning on your account stating that your email delivery is being throttled?

At Elastic Email, we continuously monitor all outbound traffic from our servers and carefully analyze feedback from destination servers processing your emails. If they request us to slow down, we comply. If they ask us to stop, we promptly suspend the delivery.

Ultimately, your reputation as an email sender - and our reputation as your email provider - depend on how those destination servers perceive your emails.

We take this matter very seriously. Receiving such a warning indicates that external servers may currently view your emails unfavorably.

Are many of your emails stuck in the "In Progress" queue in "Waiting to Retry" status, or bouncing due to "Throttled" or "Not Delivered" statuses? This often indicates that recipient servers are throttling the delivery rates. There are several ways these servers may handle the situation: they might accept the connection but "greylist" the email, or they may defer the connection entirely.

If this is happening consistently, it's likely that there's an ongoing issue with your emails that needs to be addressed (content quality, sending IP, domain reputation - these are just some of the things worth checking at that time).

Elastic Email and the recipient servers tend to throttle for the same reasons. If recipient servers throttle your email, then likely the Elastic Email system will do it too. Here are the most common reasons why your email is being throttled:

In general, if you send any unsolicited email that is not double opt-in - the email will likely become throttled and not get delivered.

We use the SpamHaus definition of Spam. Please review it. If you are continuously getting throttled, you may need to find another email provider or set up your own email delivery servers.
The Elastic Email System attempt to deliver your email for up to 48 hours. If we can not deliver the mail within 48 hours your mail will be removed from the queue. If the system determines before 48 hours that it will not be able to deliver the mail at all, it will be removed from the queue. There will not be a refund for undelivered mail, we tried, we really did, but it could not be sent. Please see our Terms of Use where we talk about using our system at your own risk.

We believe in second chances. Many users who encounter throttling are unaware they’ve done anything wrong. If you’ve started fresh, with a list of contacts who have explicitly requested emails from you, removed old or inactive addresses, added a prominent unsubscribe link, and checked your email for spam triggers, you’re well on your way to a successful campaign.

Feel free to start sending again! Our system is highly responsive, and your emails will begin to flow freely right away. You might still see the Throttle Warning at the top of your screen for a while, but as long as your emails are being delivered promptly, you’re on the right track. After successfully sending at least 10,000 emails without abuse reports or excessive bounces, the Throttle Warning may disappear, confirming that your account has been moved out of the risky pool. Great work!

If you’re confident your emails and contact lists meet the highest standards but are still experiencing throttling, don’t hesitate to contact support!

We’re here to help you succeed. Otherwise, make the necessary adjustments, and your emails should be delivered without issues. Thousands of Elastic Email customers never encounter the Account Throttled warning - join them today!