What does the term 'send throttling' refer to?

Send throttling specifically refers to the practice of controlling the number of emails sent per hour. This approach is critical in email marketing, particularly when dealing with large volumes of sends, as it helps manage server load, delivery rates, and engagement metrics. By controlling the send rate, marketers can ensure that their emails are not flagged as spam and are delivered more effectively to recipients' inboxes.

Managing the number of emails sent per hour allows for a more measured rollout of campaigns, which can contribute to better engagement and open rates. Additionally, it helps in monitoring the performance of the campaign in real-time, enabling adjustments if necessary based on the initial responses.

The other options don't align with the specific definition of send throttling. Limiting the frequency of email sends refers to a broader practice that might consider time intervals between campaigns rather than hourly counts. Reducing the size of emails pertains to file size and content management rather than send volume. Optimizing the send list is focused on targeting and segmentation, ensuring the right recipients receive the emails, which is a different aspect of campaign management altogether.