E-mail throttling is controlling the amount of e-mail 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. Throttling is an important strategy in email deliverability and can lessening the impact of complaints. For example, an ISP that sees a sender mail 10000 messages in a single hour and then sees 15 spam complaints is certain to harm your reputation more than those complaints spread out over 8 hours.
A sign that throttling may be needed is when ISP’s start publishing deferred delivery response. Additionally, throttling and experimenting with deferred sending strategies can help overcome bounce rates, spam complaints, spam trap hits, or a loss of subscriber engagement. There is no easy solution here and a Sinch deliverability expert can work with a client to manage this process.
Sinch E-mail 365 expects upstream engagement applications to handle throttling capabilities.
A sending time based delivery capability to support enhanced throttling capability is on the product roadmap.