Email provider that is official supporting keycloak or its protocols?

Hi all
I just followed this thread and got keycloak set up as IdP for my Microsoft 365 no problem, but it does not seem like its a microsoft supported usecase. Im still learning the lingo and ins’n’outs, but I think it’s just hijacking the ADFS setup configuration.

So Im looking for a “backup mail provider”, similar to exchange that officially supports Keycloak, OIDC or SAML. I tried Zoho, but I could not get it to work, it was very confusing and their documentation was lacking. Do you guys know of any?

BR
Me