It is recommended to have an email list of at least 2,000 subscribers before starting to send email campaigns to ensure cost-effectiveness. Additionally, it's important to have a clear understanding of your email marketing goals and target audience before you start sending campaigns. Take the time to plan out your content and messaging strategy, and ensure that you have the necessary resources in place to execute your campaigns effectively. Once you have a solid foundation, you can start sending email campaigns on a regular basis to engage and nurture your subscribers.