Almost every business use e-mails, it is definitely the case that no business in the modern day can exist without e-mail infrastructure existing somewhere in the supply change.
The question follows then: how does it work?
Much easier to ask than to explain! Electronic-mail (or E-mail) works broadly in the same way that a post office would. There is a sender, a recipient, an exchange which handles the mail, and where appropriate ‘proofing’ to make sure nothing suspicious gets in the post.
We’ll start with the foundation, the exchange itself.
From these, you authenticate [that is, ‘log-in’] to your e-mail server from something like Evolution. When you send an e-mail the application asks the Sendmail, Kolab, Dovecot etc. infrastructure to fulfil the request and your recipient will receive their friendly hello.
Setting up an e-mail server is not easy by any means, and is usually best left to the specialists who live, breathe and develop such email systems. We would advise you let a specialist handle the hard bits and give you the security and service required of any professional services firm.
N.B. An overview is never as much fun as digging into a system, for those more technically minded or who are otherwise just curious we would suggest looking at the project hyperlinks as above for more information.