The e-mail address is a very important aspect of every online business. We can't do the business with free email services like Gmail, Yahoo mail, etc. These free email services are for personal use only and can't be fit in business use. They have some limit on the number of emails you can send and receive per day. If you exceed their limit, they will block your email address for some period of time.
Like Search Engine Optimisation, the way emails work is a very tidy process.
Email service needs to be given a great priority as it is the only primary communication for every online business.