iMail

iMail is a lightweight yet comprehensive and very versatile piece of software that can be set up as an web or local email server. It supports unlimited email accounts, storage, and attachments.

Works with the most popular web browser and does not have many requirements

The utility is fairly straightforward to install since it does no require any Windows servers, no database and certainly no mail clients in order to make it work, with all depending on your computer's resources. You should, however, make sure that .NET Framework 4.5 or later is present on your workstation's system, before deploying it.
iMail is perfectly capable of working on all modern and most popular web browsers out there, namely Microsoft Internet Explorer, Google Chrome and Firefox.

Deploying it requires a bit of attention

To get started, download the provided package and swiftly install iSanwhole Data Center. Before anything, head over to the Install iSanwhole menu and select "Install IIS." Afterward, extract, install and start the iSanwhole package from the same menu.
To start learning the tool, you can easily test it by doing the following. In the "Accounts" section, use the contextual menu and select "Create Test Accounts Simple" and use the default password, namely "111111" (six ones).
Similarly, select "Create Test Mails" and start thoroughly testing it by starting your computer's default web browser and by entering the server's IP address.

Non-complicated, web-based user interface

You should be able to see the actual iMail web-based interface which is, by all accounts, a fairly straightforward one. In addition, it features the same layout you are probably used to from any other, typical, web email service out there.
As expected, from the left side of the browser's window, you should be able to compose new emails, as well as check the Inbox, Sent, Archive, Important, Spam and Trash sections. Evidently, the emails can be categorized, moved from place to place and thumbnails, audio and video content should be all previewed without problems.

iMail - comprehensive email system for businesses or schools

All in all, if you want a capable, almost-no-maintenance, self-hosted server for both LAN and WAN, with support for unlimited mail accounts and storage, and you don't mind dealing with a web-based interface, then you should, by all means, give iMail a quick try-out.