Some sites mount each user's home directory from a local disk on their workstation, so that local access is fast. However, the result is that .forward file lookups are slow. In some cases, mail can even be delivered on machines inappropriately because of a file server being down. The performance can be especially bad if you run the automounter.
The ForwardPath ( J) option allows you to set a path of forward files. For example, the config file line
If you create a directory such as /var/forward, it should be mode 1777 (that is, the sticky bit should be set). Users should create the files mode 644.