Email throttling is controlling the amount of email messages sent to one ISP or remote server at one time. Sometimes ISPs block messages when a high volume is sent by one sender at one time because they might be concerned its spam. While this may seem somewhat restrictive, it does provide senders with some unique opportunities.
Spreading out the email delivery of your messages has it benefits. For one, you can regulate how many emails are delivered during high-traffic periods. This can help maximize response to your email campaigns and provide fertile testing ground for future sends. Alternatively, throttling can help you manage responses. For instance, if your call to action is a phone call, you can better manage call center traffic by staggering your email communication. Likewise, you can better manage server bandwidth to your website when marketing special promotions and sales.
However, if you are a high volume sender whose business model relies on timely delivery to reap the maximum response, then throttling (or rate limiting) can prove to be a hindrance. Daily deal sites are a great example. They have a short window of opportunity to achieve sales and therefore need all of their email messages to reach their subscribers right away. In this case, your email reputation plays an important part in determining delivery. Since ISPs impose strict standards on mailers they suspect to be spammers, following best practices and working with an experienced email provider can make a big difference in how ISPs treat your messages.
To learn how SendGrid handles throttling, click here.