I have migrated to Linux for app and DB servers, but I don't know of anything better than Active Directory for managing users or Exchange for email. I'd have t

I have migrated to Linux for app and DB servers, but I don't know of anything better than Active Directory for managing users or Exchange for email. I'd have to imagine such things exist, (I mean, come on it's 2016 there has to be a reasonable alternative to Exchange at least by now, and something a little better than raw LDAP for user management, right?) I just cut my teeth on a MS environment and don't yet see anything comparable.