Which are the best email marketing service providers for small business?

Email Marketing is one of the effective online marketing methods to outreach your small business. When you are deciding to do email marketing, it’s essential to choose an email marketing service that helps to achieve your business's requirements and wants. Email marketing services include free trials, a range of email templates, email scheduling and social media integrations. I would like to know about the best email marketing service providers for small business. Can you guys tell me which are the best email marketing service providers for small business?