Ok... all over the place, with one direct answer
IP addressing, basic routing, etc. are all covered in other courses, some taught by the person that developed a lot of Cisco's training materials.
If I were to have them install a web front end to do it all, I'd use ISPConfig
We have a "Linux Admin" course (I'm the only teacher for it) and we cover what Open Source/Free Software is, what Linux is (and isn't), what a Linux distribution is, how hardware is handled, disks and partitions, device files the /dev and /proc directories, editing text with joe vi/vim and nano, all sorts of command line stuff, working with tar.gz and tar.bz2 files and compression in general, file permissions, user and group management, differences between su and sudo and when to use which, shell scripting, installing applications from source or using the package manager or precompiled binaries in some form the package manager doesn't use (tar.gz, etc), network configuration, network utilities, iptables. Only services covered are in a homework assignment to find out what network ports are used and 2 different how-tos on configuration for SMTP w/ both Exim and Postfix, mysql, samba, ftp with proftpd or vsftpd, pop3 with courier or dovecot, imap with courier or dovecot.
So... this second class is focusing on services, called "Internet Services with Linux" - we've *never* taught students in our network services track how to install and configure mail, dns, pop3, imap, mysql, LAMP w/ name based virtual hosts, dhcp, etc. Well, I guess DHCP and DNS are covered a little bit in the Windows Server class....
So the second class is started with a quick review of the system commands from the first class, installing software (source, package manager, binaries in non-package), and shell scripting. Following that (that's where we are now), we'll install a command line only Debian server in VirtualBox and configure it as a DHCP server, DNS server (both caching and authority for a demo domain), and gateway for a desktop system (also in VBox). Then we'll add a second server as a Samba server and do a basic stand-alone file server configuration. Then students will activate VPS accounts and we'll install apache and do a full LAMP set up with name based virtual hosts. We'll add extra users to the mysql side and manage their permissions, and due to Oracles behavior of late we'll talk about MariaDB as well. Then we'll add email services - SMTP with either Postfix or Exim (hence my original post), POP3, and IMAP with both real users with local system accounts, virtual users/domains associated with system accounts, and virtual users/domains with no local user account (Postfix can do this with db storage, dunno if Exim can). SSL will be discussed the whole way, but since there is an extra cost for the certificates we'll either use self-signed certs or just talk about it.
So... Postfix or Exim? Due to the virtual users w/ no local account part of mail setup, I'm leaning very heavily towards Postfix... and together they take about 70% of the SMTP hosts out there... but Exim has about twice the numbers Postfix does. I've used both, and have no personal bias towards one or the other....