If you’ve ever tried to set up your own mail server, you know it can be a pain in the ass.
A lot of hosting companies offer free email forwarding and this may work fine for you, but if you want a separate mailbox (or several) you either need your own mail server or you need to get someone else to host it for you. Google used to offer free email hosting (i.e. gmail, but with your own domain name), but stopped offering this for free in 2012. Outlook (from Microsoft) stopped allowing new sign ups with your own domain name too.
Fortunately, Zoho offers free email hosting (and paid plans, of course). As of the time of writing, they offer free email hosting for 10 users, 5GB per user.