* Parses/consumes QWK headers.dat files
  - No more to/from/subj length limits
  - Extensive header details transferred for each message
  - IP/hostname filters (.can files) are applied to appropriate header fields
  - Code cleanup in the QWK functions
* New functions to read/parse/search filter (.can) files as string lists
  - Performance boost - no need to open/read/close .can file for each message
* More thread-safe Message-ID retrieval/generation (ftn_msgid and get_msgid)
* Better Message-ID generation for misconfigured systems (e.g. no hostname)
! These changes require the latest smblib and xpdev libraries !

startup option - we will *always* use the local timezone. If the sysop wants to
use GMT/UTC, they should configure their operating system accordingly.

server.

This allows using a private DNS server when an external interface is specified
(ie: DNS Server of 127.0.0.1 with an interface address specified)

of recipient mail addresses (for Deuce).

not have the default entry (*.synchro.net) allow SPAM from DNSBL-listed servers
sending MAIL FROM <spammer@yourbbs.synchro.net> to sysop@yourbbs.synchro.net
A dnsbl_exempt.cfg entry of "*.synchro.net>" would be required to match
<spammer@yourbbs.synchro.net>

address (reverse path) is listed in the dnsbl_exempt.cfg (without the <>), any
positive DNSBL result on the sender's IP address will be ignored.
* Automatically adds ("white-lists") recipients of mail that was successfully
delivered by the sendmail thread to the dnsbl_exempt.cfg file if they're not
already listed.
* Local submit performance improvements: don't perform ip.can, host.can or
spamblock.cfg searches or DNSBL server queries for local connections (from
localhost or the same IP as the server is listening).

Change block filename to 0001.smtpblock
Facebook does not allow a # in email addresses but does allow a %.

Incoming email is now scaned for To: headers in the format <name>#<tag>@host

Tag is extracted, and if it is not found in data/user/%04d.smtptags it is
sent to the user.  If it DOES match a line in the smtptags file, the email
is rejected with a no such user error.

Using this allows you to easily create "temporary" email addresses.  Once you
start recieving spam on one tag, just disable it.

TODO: Make the separator characters configurable.

identically to the SMTP transfer port (e.g. TCP port 25).

That was WRONG.

enables read & write permissions for user & group & others.

determines if the specified user can post msgs on the specified sub-board,
and optionally returns the reason (text.dat item number) indicating the reason
why not (if it returns false).

Remove time32str()

auto-detected DNS server IP address, the DNS server address was blank in
the error log message.

Removed unused recycle_sem code.

Also, when sending mail, the bind() call doesn't specify a port, so there
is no need to ask for root.

for messages being forwarded to external Internet e-mail addresses.

number (e.g. '1'), and the RX_BY_NUMBER mail server option was disabled, then
the mail would be rejected with "user unknown".
"name aliases" weren't effected by this.

(in sbbs.ini [mail] DefaultCharset), then not used.

(would still accept the message).
Added 'To' header field checking against email.can file (for Sniper).

"postmaster") unless the ALLOW_SYSOP_ALIASES option is enabled
(disabled by default) or the alias is specifically listed in the ctrl/alias.cfg
file.
Also, if the alias.cfg file correlates a user *number* with an alias, support
receipt of mail to that alias even if the RX_BY_NUMBER option is not enabled.
This allows us to use '1' instead of 'sysop' in the default alias.cfg file.

e-mail address.

permissions on *nix possibly making untouchable later.

error and is fairly common on Linux.

Since the only way to correcty detect NPTL is at *runtime*, add that
detection in to main() and honour it throughout.  sbbscon.h makes the
thread_suid_broken variable/macro available to other files which need it.