A seed list in email marketing refers to a carefully curated list of email addresses that are used to test and monitor the deliverability and effectiveness of email campaigns. These email addresses are typically owned by the sender or a trusted source and are strategically placed within the email list to ensure that the email reaches the intended recipients and does not end up in the spam folder. Seed lists are an essential tool for email marketers to gauge the success of their campaigns and make necessary adjustments to improve their overall email deliverability and engagement rates.