If your email marketing campaigns do not include an unsubscribe option, it can lead to several negative outcomes. Firstly, it may damage your brand reputation. Customers who feel trapped without an option to opt out are likely to view your brand negatively. Secondly, it increases the likelihood of your emails being marked as spam, which can harm your email deliverability rates. Internet Service Providers (ISPs) use spam complaints to filter emails, and high complaint rates can lead to your emails being blocked.