nfs_flush_chown_uid errors over NFS

Hello all,

We use an older version of dovecot 2.0.19 on Ubuntu 12.04 using an NFS share, also a linux box.

Now we want to migrate the storage to a FreeBSD server and later on the mailservers them self. In the firsts test all looks fine, but we do see some errors some times. Error: nfs_flush_chown_uid: chown(/var/mail/virtual/domain.com/user/Maildir) failed: Invalid argument

This does not happen all the time but sometimes it shows up. I can read all the mail using an mailclient and the uid shows the user vmail:vmail.

Is this cosmetic or is there something wrong?

Thanks for your time Regards johan