Zoho Mail Forever Free Plan

Zoho Mail - 'The Forever Free Plan' - is currently available in the US, EU, and India data centers only. Your IP address determines to which data center you are allocated. For example, I am in UK, and have been allocated to the Amsterdam (The Netherlands) data center.

Go to: https://www.zoho.com/workplace/pricing.html

Scroll down towards the end of the page:

Screencap of the Zoho Workplace web page
Screencap of the Zoho Workplace web page

Click on the 'Sign Up now' to proceed. Because I'm in UK, I've been directed to the zoho.eu sign up web page: 

Screencap of the Zoho Mail sign-up page
Screencap of the Zoho Mail sign-up page

At this point, you need to choose the 'Business Email' option, to be able to use your own domain. The 'Personal Email' option only offers a zohomail email address.

Complete all required fields, including your 'mobile number' to proceed.

Once all is completed, you're allowed to use only one own domain, but can create up to 5 users (5GB storage per user) for that domain.

As with any new provider, it takes time to become familiar with the UI, set up the domain DNS records, users, etc.