Some versions of Unix or implementations
of disk I/O do not support immediate updates of directories when the
data on them changes. The ReiserFS and
Ext2fs filesystems are two such implementations.
Linux is one such operating system. For these, this
REQUIRES_DIR_FSYNC compile-time macro is set to true, which causes
sendmail to fsync(2) the
directory every time it is updated.
In the event you need to port sendmail to a new
operating system or to a new filesystem, you might need to set this
compile-time macro to true. The way you set it to true looks like
New ports should be reported to
email@example.com so that they can be folded
into future releases.