If anyone is interested: here's a document that describes how to set up NIS for providing automount information. It now works for me.
For myself I'll give up this solution since in my domain users get authenticated by Active Directory (LDAP) so the automount information must come from there too. There are nice HOWTOs that decribe how to do it with LDAP but not with AD which differs from LDAP. E.G. you can't include schema extensions. Changes on the AD schema are irreversible, unlike LDAP. Doesn't sound like fun, does it? It was very nice if someone who has experience with modifying the AD schema could give some hints on how to put a LDAP schema into AD.
...although I doubt there are any people knowing much about Microsoft AD