You might like Migadu[0]. Its set up as more of a postmaster tool but does have webmail, and multiple accounts on a domain is a first-class feature. I found out

You might like Migadu[0]. Its set up as more of a postmaster tool but does have webmail, and multiple accounts on a domain is a first-class feature. I found out about it from ddvault's recommendations[1]. [0]: https://www.migadu.com/ https://www.migadu.com/ [1]: https://drewdevault.com/2020/06/19/Mail-service-provider-recommendations.html https://drewdevault.com/2020/06/19/Mail-service-provider-rec...