What is Microsoft Exchange?

It is a mail and calendaring server developed by Microsoft. It works only on Windows Server operating systems. It initially supported only MAPI protocol but later on it also added support for POP3, IMAP, SMTP, and EAS. It is licensed both in the forms of software as a service and on-premises software.

Exchange provides  a management solution that allows a company to have its own mail system without needing any of the external mail providers. It also provides integration with Active Directory which enables a company to create accounts that allow its employees to use its resources while also offering them mail services at the same time.