There are 6 main types of emails for email marketing: welcome emails, offer emails, value/reorder emails, survey emails, product launch/announcement emails, and breakup emails. Effective email marketing requires putting in work on content, time, and money. It is important to avoid exclamation marks and block letters in subject lines, conduct A/B or multi-variate testing, only use opt-in subscribers, include an unsubscribe link that works for 30 days, provide contact details, and have sincere and valuable content.