How can I set up Email accounts on my domain and use RoundCube for managing mails? + Send mails (SMTP with PHPMailer)

I’m normally used to using cPanel and that kind of stuff, so I’m pretty green to Ubuntu and managing stuff myself, but you gotta start somewhere.

Anyway, I would like to set up email accounts on my domain which I had on my previous server. Such as this: contact@domain.com admin@domain.com etc…

I have been reading around for some info about this, for example this tutorial: https://www.digitalocean.com/community/tutorials/how-to-install-your-own-webmail-client-with-roundcube-on-ubuntu-16-04

But I’m unsure whether or not it will meet my needs, first of all the Roundcube needs to be installed on mail.domain.com or domain.com/roundcube, and NOT on root domain.

I also need to use SMTP for sending out verification mails such as Registration Welcome, and reset mails. For this I have used PHPMailer on my previous server, but how do I go about setting up SMTP on my web server? So emails are sent from noreply@domain.com etc.

My droplet is running Ubuntu 16.04 with LAMP stack installed.

Any help is appreciated.