Ask HN: Provide a small email account to your users?

I have a "cool" domain name in my niche and I'd like my users to use it as an email address. I was looking for a SaaS or web service (even if I have to pay a monthly fee) that would allow me to provide free email accounts for that domain, including sign up, login and a web browser client.

I remember yearrs ago (more than a decade) than zzn.com offered something liek that, but I couldn't find any modern service. Is there a way? I dont want to create myself the accounts manually.

PS: I know my users wont use this email as their primary email address and I would not recommend it either.