> Also, what considerations are there for file locking or other potential
> problems when running Postfix with a Netapp-style box for /var/mail
> delivery?  I know that FreeBSD has broken NFS file locking (both client
> and server?) but I'm not sure if this is something Postfix can work around
> or not.

Postfix jumps several hoops in order to deal with NFS-specific
problems. Thus, Postfix on NFS is slightly less reliable than
Postfix on a local disk. That is not a problem in Postfix; the
problem is in NFS and affects other MTAs as well.

For queue locking, NFS is not an issue because you cannot share
Postfix queues with other Postfix instances.

In order to have mailbox locking over NFS you have to configure
everything to use fcntl() locks for mailbox access (or switch to
maildir style, which needs no application-level lock controls).

To turn on fcntl mailbox locks with Postfix you specify:

    virtual_mailbox_lock = fcntl
    mailbox_delivery_lock = fcntl

This is useful only if all mailbox access software uses fcntl()
locks.

You can also "play safe" and throw in username.lock files:

    virtual_mailbox_lock = fcntl, dotlock
    mailbox_delivery_lock = fcntl, dotlock

this is the mix that many applications end up using.
