tuning of queueing functions as recommended by John Gardiner Myers
<jgm+@CMU.EDU>; return mail headers (no body) on messages with negative
precedence; minor other bug fixes

Release 6

dynamically allocate header fields (and more....); miscellaneous
cleanup (mostly comments)

(partially) ANSI-fy it

security fixes: check mode and owner of qf files

a variety of bug minor bug fixes; add file locking when writing
to a UNIX file; strip out dangerous envariables

do clean connection closing on queue runs

fix bogus envelope problem in clock-driven queue runs; misc. fixes

miscellaneous changes to improve logging and messages

lint

reduce number of instances of CurEnv by passing it as a parameter

many fixes to controlling user code; fix Neil Rickert's hack using
CNAME for someone else's host

clean up controlling user implementation; all those global variables
weren't needed

open connection caching

make C option safe; output values of $r and $s macros to qf; allow
long messages in queue files

try to eliminate some of the CurEnv globals

convert lockf implementation to use fcntl directly

fix race condition in queue file locking; generalize getla

fix lockf code; have getcanonname recognize canonical names

oops.....

hacks for systems with lockf, not flock

k option specifies checkpoint interval (default 10);
qf file is rewritten after k successful deliveries.
(ref bug 4.3BSD-reno/usr.bin/10)

ANSI

new copyright notice

fixed a race condition in the locking when there are LOTS of queue runs