Some people unsubscribe immediately because they only wanted the free item and were not interested in further emails. Others may leave because the follow up message does not match what they expected. If the freebie focuses on one topic but the emails talk about something different, readers lose interest quickly. A simple welcome email that explains what messages will come next can help avoid confusion. Some people also begin with a lighter pace so readers do not feel flooded with content. Clear communication from the beginning makes a difference because it prepares people for what they will receive. What other reasons have you seen that cause people to leave so quickly?