fastforward handles qmail forwarding according to a cdb database. It can
create forwarding databases from a sendmail-style /etc/aliases or from
user-oriented virtual-domain tables.

fastforward supports external mailing lists, stored in a binary format
for fast access. It has a tool to convert sendmail-style include files
into binary lists.

fastforward is more reliable than sendmail. sendmail can't deal with
long aliases, or deeply nested aliases, or deeply nested include files;
fastforward has no limits other than memory. sendmail can produce
corrupted alias files if the system crashes; fastforward is crashproof.

fastforward's database-building tools are much faster than sendmail's
newaliases. Even better, fastforward deliveries don't pause while the
database is being rebuilt.

fastforward does not support insecure sendmail-style program deliveries
from include files; you can use qmail's secure built-in mechanisms
instead. fastforward does support program deliveries from /etc/aliases.