There are a few places where your email "delivery" rate can be throttled.
Between your system and ours
As you may know, Elastic Email is an all-in-one email delivery platform. We offer an SMTP Relay and HTTP API as well as the User Interface to submit emails. For users that connect and send via the SMTP Relay and HTTP 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 make sure not one single user can abuse or dominate the SMTP and API submission servers. We also recommend setting any connection timeout settings to at least 30 seconds.
Elastic Email System Throttling
Have you ever seen a warning on your account that your email delivery is being throttled? Elastic Email carefully monitors all outbound traffic from our servers and listens carefully to the responses we are getting from the destination servers who are receiving your email. If they tell us to slow down, we slow down, if they tell us to stop, we stop. Ultimately, your reputation as an email sender and our reputation as an email provider is based on what those destination servers think about your mail.
We take this very seriously. If you received this warning, it means that your email is not looking very good to the outside world right now.
Recipient Server Throttling
Do you have a lot of emails sitting "In Progress", "Waiting To Retry", or are bouncing due to "Throttled" or "Not Delivered"? This can mean that the delivery rates are being throttled by the recipient servers. There are a couple of ways recipient servers handle this. They may accept connections but "greylist" the email or they may defer connections altogether.
If this is consistently happening to your email then there is likely an ongoing problem with your email that needs to be fixed.
What causes my email to be throttled?
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 too and vice versa. Here are the most common reasons why your email is being throttled:
This is the easiest way to get throttled. Elastic Email has a very low tolerance for Abuse Reports and so do recipient servers. If your contacts complain/report your email then your email may become throttled and may not be delivered. You will get abuse reports if your email is unsolicited, not double opt-in or does not have a working unsubscribe link.
Sending to invalid email addresses, or old email addresses
This one is very serious. If you send email to old, inactive email addresses, even if they signed up for your service they may now be spam traps. This can get our IP blacklisted and will definitely lead to throttling of your mail. Don't send an email to email addresses if you haven't sent mail to them for more than 1 year. Period. 6 months is better.
Sending poorly formed content
Make sure you run your content through a spam checker before you send it. This is particularly important if you are in an industry which is generally associated with high spam volumes such as Mortgage Lending / Real Estate, Gaming, or Affiliate marketing. We run some automatic spam checking on your email.
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.
We're firm believers in second chances. Many people who end up throttled did not know they were doing anything wrong. If you have started with a new list of only people who specifically requested email from you, cleaned out all the old or inactive addresses, added a very big, bold, unsubscribe link and ran your email through a spam checker then you should be on the road to a successful email campaign. Feel free to start sending again. Our system is very very responsive and your email will immediately start to flow freely. You may still have the Throttle Warning at the top of your screen for a while, but if you see that your email is going out quickly, you'll know that things are going ok. After you have sent at least 10000 emails successfully, without abuse reports, or too many bounces, you may see the Throttle Warning disappear and you will know you have been moved up and out of our risky pool. Great job!
If you are sure your email and contact lists are up to the best standards but are still being throttled, then contact support. We are understanding people who want you to succeed with us. Otherwise, make some changes and your email should be delivered without the problem. Thousands of Elastic Email clients never see the Account Throttled warning.