Apple Mail is the default Email client on all the Mac OS based computers. Apple Mail is one of the versatile email clients that enable to work with multiple accounts at once. It has integrated search feature, so it's easy to find emails. It also has other features like support for Passbook.
It has a modern interface, which is Graphic User Interface. It supports EWS, iCalendar, IMAP, LDAP, POP3 and SMTP protocols etc. Apple mail is fully Mac OS based email client.