By default root on a client is mapped to user nobody on an NFS server.
This is a security measure. However, this may mean that
evolution, for example, will not be able to read NFS
mounted mail directories (i.e., where on machine Cultus (97.20) you
mount /var/spool/mail from, for example, Altrop (97.21)).
evolution
(or something used by evolution)
seems to be root when accessing the email. The solution is to allow
root mapping to root for this export from Altrop (97.21). Thus, on
Altrop (97.21) ensure the following exists in /etc/exports: