try to eliminate some of the CurEnv globals

properly set up envelope when returning email

reject connections more quickly if load average goes up;
try to time out on opens of .forward files on hung filesystems

check for configuration level higher than we understand

print host name in debugging info

partial hooks for caching all email connections; won't work
because it could result in too many connections, and some could
time out.

check I/O status when appending to files

allow on-line comments; don't double-parse RCPT To: addresses;
warn on truncated lines; do some sanity checks on .cf file descriptor

add new 'V' config line to control configuration syntax version

from Bryan Costales: several smallish changes, mostly to clean
up debugging output. The major change is that test mode (-bt)
doesn't automatically run through ruleset three any more.

drop mode a (ARPA FTP) -- NCP is gone forever.....

clean up #ifdef configuration to more cleanly match the modern age

allow limited 8-bit support; allow [TCP] as an alias for [IPC], even
though it's wrong; restore t option for System V support; add L=_N_
mailer option for line lengths; implement R mailer flag to get

allow limited 8-bit support; allow [TCP] as an alias for [IPC], even
though it's wrong; restore t option for System V support; add L=_N_
mailer option for line lengths; implement R mailer flag to get
restricted port; misc cleanup

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include defaults for SendMode and ErrorMode; never ignore single dot
termination when collecting message in SMTP mode.

mark tempfail during initial usersmtp open to avoid extra connections
in the future

allow F config line to open a pipe

print some control characters in xputs

don't set FullName in daemon run

set close-on-exec flag for recipient log file

add -R flag to log incoming raw recipients for analysis

add ENOSR (no streams resources) to list of temporary failure conditions

<sysexits.h> before "conf.h"

clear errno after trying to open the database list

clear errno at top of loop to avoid bogus messages

drop STATIC