When any enterprise hosts on a cloud server, you will definitely need an email server to be hosted. Many cloud hosting providers now offer domain name along with email servers.
With email hosted on your cloud server, you can choose many features such as if you want to keep your data on the server or on your local machine. You can also install many open source free softwares and migration of emails are easier with lcoud servers. Also, cloud hosting providers also offer free upgrades and custom-branding on your own email server.