Emails are sent in batches to help build a positive reputation with email services and reduce the risk of messages being flagged as spam. In the beginning, the system starts with smaller batches so email providers can recognize and trust the sending domain. As you continue sending more campaigns and build that trust, the batch sizes and sending speed will automatically increase—meaning your emails will go out faster and more efficiently over time. If you’re sending to a large list, it may take a few hours for all messages to go out, but that’s completely normal and nothing to worry about.