Can't see it on your site as registration is disabled.

Link above will take you to it without being registered. The login screen you see on that he page is the login screen to the member mail. It will not work for you to use, you will need to set it up on your site with the email accounts you created within your domain.
I have been using it for years.
Note: Registration is now on, though there is no need to register unless you want to.
If you want to test it out on my test site, I will set up a testaccount@blind-eddie.com email address if you want.

@eddie, it's not a free version, as it expires after 30 days! :(

No, there is a free version of lite & pro, I use both & they do not expire.
You can use any one of the webmail scripts in the google link I posted above to create your page with, I only posted an example of what I am using & have been using for a few years now, for free.

Download AfterLogic WebMail Lite, a free open-source webmail front-end which allows users to send and receive e-mails via SMTP, POP3 and IMAP protocols.
Google is your friend....After logic free search

You are allowed to download and use Webmail pro for free for up to 5 users with unlimited email accounts each.
I also have this installed and using it for the many @my domains email address I have.
You may have to contact them regarding this.
AfterLogic Announces Free WebMail Pro 5-user License
I know I can use yahoo, gmail, hotmail, ect... to add all my @my-domain email addresses to, I just like this better