Some of these are going to be obvious, and are quite probably on the roadmap anyway, but…
- Mail
- SMTP/IMAP (and I guess POP, but that should have died the death many years ago)
- Virus scanning
- Spam filtering
- Webmail (I love Horde, but it’s looking increasingly like abandonware)
- DNS
- Feature parity with NS7 would be a minimum, but a full-fledged DNS server would be better
- Option, at least, to be the public authoritative DNS server for your domain
- Integrate with Mail to add the dozens of DNS records a proper mail server really needs
- …and if it’s the public, authoritative DNS server, it can also be used for ACME validation
- Technitium would seem to fit the bill here.
- SSO
- LemonLDAP::NG is available as a Docker container and seems to be working well
- Though really, IMO, if used, this ought to be part of the core distro, and then configure other applications to authenticate against the SSO provider, rather than against whatever LDAP server that SSO provider is using.
- Nextcloud is already there. Assuming that Collabora/OnlyOffice are also available, all good there.
- Matomo
- I run mine on a separate VM, but Zabbix.
- General web hosting with the LAMP stack
- CMSs