Messages posted to sub-boards via SMTP normally will have the recipient
name/address as the "To" (RECIPIENT) value of the posted message. If the sysop
wishes to replace this string (for all SMTP-posted messages) with a different
string (e.g. "All") this is the setting to allow that.

I do want web-scrapping spammers to collect the 'to' fields for my TLDR and
Coverity-scan posts and post their own spam messages via email (any more).

Also accommodate the new link list API (long -> int).

White-space changes only, exception being the rare insertion of NL before
closing brace (couldn't find the option to disable that behavior).

I excluded some header files (e.g. sbbs.h) since uncrustify seemed to be doing
more harm than good there. I might just end up applying different set of rules
to .h files.

By default, the duration is infinite, but some sysops may not want this
file to be ever-grower but rather periodically pruned by the new trashman
utility.

Sysop that don't use spambait.cfg won't benefit from this change.

Still using BOOL where we need Win32 API compatibility.
Using JSBool instead of BOOL or bool where it matters.
Changed most relevant TRUE/FALSE to true/false too (though it's not as critical).

You shouldn't need to #include <stdbool.h> anywhere now - gen_defs.h should do that automatically/correctly based on the language/version/tool. In C23, stdbool.h isn't even needed for bool/true/false definitions (they're keywords), so we don't bother including stdbool.h in that case.
Microsoft didn't define __STDC_VERSION__ in their older tool chains (even though they were C99 compatible and had stdbool.h), so we use a _MSC_VER check to know that there's a stdbool.h we should use in that case.

For other/old compilers (e.g. Borland C) we #define bool/true/false following the pattern of stdbool.h (doesn't use a typedef).

I didn't convert UIFC yet.

This addresses issue #698

[integerOverflow]

It is almost 2024 after all. :-)

The notification of offline users was removed from the mail server 13 years
ago (commit 729eb16b) without a lot of fanfare or explanation. Add an
option for notification of offline users (in addition to online users) for
those sysops that want that behavior.

Use the userdat is_user_online() function in place of the getnodedat() loop,
which also wasn't considering nodes in "logon" status as having a user online.

The only difference in the data/scheme is that the "error" topic (error log) is now under each server rather than each host. I don't *think* there are any other changes from the MQTT consumer side.

Still not done: subscribing (e.g. support for recycle or node-spy-input via MQTT) and NT services support.

This change also includes a cool feature that will prompt the sysop if there's a timeout (30 seconds) while waiting for servers to shutdown gracefully and giving the sysop the option to abort (Cancel) the wait (and shutdown ungracefully) or continue the wait (OK).

Requires libmosquitto (e.g. install mosquitto-dev pkg) and set
in ctrl/main.ini:
[mqtt]
Enabled=true
broker_addr=127.0.0.1
broker_port=1883
qos=0
keepalive=10

Next up: Windows support

When the systemd dev package (e.g. libsystemd-dev) is installed, we can use
sd_notify() to inform systemd of Synchronet server state/status. The state
values (READY, STOPPING, RELOADING) are "well known" while the status
value is a free-form text string (the last lputs output).

Eliminated the free-form status() callback from *startup_t.
Eliminated the now-redundant started() callback from *startup_t.

Eliminated the use of sbbs_status.c/h as nothing is using that interface
and while I do plan on using a remote control/monitor interface, I'm
considering use of a standard pub/sub lib and protocol.

This commit is going to break the Windows sbbsctrl build for sure.
Probably break the sbbsNTsvcs build.

- InternetMailReceived
- InternetMailForwarded
- FidoNetMailReceived
- WithAttachment
- FidoEchoMailReceived

For The Millionaire, closing issue #254

The first string (suppressed with %.0s) is an optional date/time stamp.

This also deprecates (removes support for) the [mail] NewMailNotice and ForwardNotice keys from sbbs.ini.

Allow a configured maximum-severity (minimum value) for TLS-related log messages. Default is 0 (LOG_EMERG, maximum severity).

Getting tired of SMTP/TLS (SMTPS) related errors clogging up my inbox. I'm setting this to "Warning", like I did for [web].

A "hack attempt" sound file is now supported in the Terminal Server, Mail Server,  and Services.

"login" and "logoff" sound files are now supported in the Terminal Server, FTP Server, Web Server, Mail Server, and Services.
This enhancement fixes Issue #157

The following sound files may now be configured in the [Global] section of the ctrl/sbbs.ini file, if desired to set the default sound files for all servers/services in on place:
- AnswerSound
- LoginSound
- LogoutSound
- HangupSound
- HackAttemptSound

The default character set for outbound mail is now auto-determined (when not explicitly specified for a message) between UTF-8, ASCII, and CP437. The [mail] DefaultCharset setting (which fell-back to iso-8859-1 if blank) is no longer "a thing".

Also: specify 8-bit content-transfer-encoding for the (potentially UTF-8 or CP-437) plain text portion of a MIME-encoded message with file attachment (7-bit was wrong) and pass down the text sub-type (e.g. could be "html") for inclusion in the mime-part header (don't assume text/plain, but still use that as default).

Also: log an error when failing to delete an attached file (e.g. from data/file/*.out).

The mail (SMTP) server is a popular target of bots. Impose a maximum-concurrent-connections limit (optionally). Similar to the terminal server option, except, don't deduct the number of authenticated connections (I can add something like that if desired). The new config option is [mail] MaxConcurrentConnections in the ctrl/sbbs.ini (defaults to 0, no maximum).

Fixed error responses in mail_server accept loop: was always sending POP3 error responses even if the connection was SMTP.

Cleaned-up the service/port checking/logging in the mail_server accept loop: no strcmp() needed, log the protocol name (e.g. "SMTPS") instead of the service name (e.g. "submissions").

Fix age-old bug with Borland/C++Builder built executables (Windows):
to achieve compatibility with  the default __cdecl symbol naming rules of
Visual C++, we were using __stdcall convention for DLL functions when
building code with Borland/C++Builder tools and using the default (__cdecl)
convention when building with Microsoft (Visual C++) tools. Although this
allowed symbols to be located when linking, the calling convention mismatch
caused a stack cleanup issue that very rarely manifested itself in a bug
(e.g. exception of some kind in sbbsctrl.exe, usually). Mismatching
the calling conventions was unintentional (I thought the default for MSVC
DLL functions was __stdcall) - but since the calls to MSVC-Built DLL functions
worked 99% of the time, I didn't realize there was an underlying issue. So I
now work-around the DLL symbol naming mismatch using a command-line option (-a)
passed to implib in src/sbbs3/ctrl/makelibs.bat

I had previously worked-around exceptions when calling MSVC DLL functions in
sbbsctrl.exe by calling the problematic DLL functions from a timer tick handler
rather than a user control (e.g. button) event handler. Those work-arounds can
now be removed.

The erroneous "DLLCALL" definition design pattern was replicated (copy/pasted)
to many other projects' header files in cvs.synchro.net. In the future, we may
want to just remove all instances of *CALL since they now serve no purpose and
appear as useless "Kruft" (but do allow us to more-easily globally change DLL
function calling conventions if/when necessary in the future).

The "official" log line format is (as of right now at least):
"[socket] [protocol] [user/host-ID] [! if error]message"
Hopefully I can remember that when I add new log messages.

Also setting the protocol to SMTPS, POP3S, SEND/TLS, when appropriate and
passing it around to pretty much any function that can log a message.
Added debug-level log output when the mail sever is sending message body text
(every 100 lines).

and resolve the resulting warnings.

mail_close_socket() also destroy the session, and take pointers to set the
socket to INVALID_SOCKET, and the session to -1.

for new TLS-related settings:
SubmissionsPort -> TLSSubmissionPort
POP3SPort -> TLSPOP3Port
USE_TLS_SUBMISSIONS_PORT -> TLS_SUBMISSION
USE_POP3S_PORT -> TLS_POP3
There was actuall a typo in the "USE_POP3S_PORT" string anyway. <shrug>

section:

POP3SPort=995
SubmissionsPort=465

And two new mail options:
USE_SUBMISSIONS_PORT
USE_POP3SS_PORT

These are the last of the two option bits for the mail server.

Support STARTTLS in SMTP and STLS in POP3.  This includes the sendmail
thread.  Clients can now be configured to use STARTTLS with Synchronet
mail services, and Synchronet will attempt to deliver securely when
possible (though it will fall back to plain text delivery when necessary.)

This touches a *lot* of mail server stuff, so some instability is not
unlikely.

Of course, RFC8314 (Jan, 2018) officially recommends implicit TLS on the TLS
ports now, so support for that should be next.

will set the "KILLREAD" attribute flag on any SPAM-tagged email messages so
that after they are read (or downloaded via POP), they will be auto-deleted by
smbutil maintenance. Defaults to off.

are now configurable via the following news keys in the [Mail] section of the
sbbs.ini file:
	NewMailNotice
	ForwardNotice

Using the newly updated string literal support to allow for Ctrl-A codes using
C charater literal notation (\1) for control-A codes and standard C-escaping
of carriage-return (\r), line-feed (\n), etc.
Beginning and trailing space characters are also preserved (if specified) in
the key values.

The default strings are updated/different from what was previously hard-coded
in mailsrvr.c. If you want the local timestamp (back) in the notice, change
the '%.0s' in the default string to just '%s'.

By default, after 20 consecutive (unique) failed login attempts, *or*
a failed login attempt wtih a name from the name.can filter file.
The default temporary ban duration is 10 minutes.
The temporary ban thershold is configurable via LoginAttemptTempBanThreshold
in sbbs.ini and the ban duration is configurable via LoginAttemptTempBanDuration
(in seconds).

a socket (and returns void), but mxlookup.c did not know this because it had
its own prototype for this function (lazy, I know).
- moved the prototypes for mail_open_socket and mail_close_socket to mailsrvr.h
- use socket() to create the (single) socket (is not a multisock, does not do
  IPv6)
- this was the cause of the "getting socket option type" errors in the
  error.log that began showing up recently. Good thing it had a "LOG_ERR"
  log level or I probably would not have noticed for a long time. :-)

before re-reading them.

xpms_add_chararray_list instead.  Prevents having to free string lists
in the sbbs.ini parsing code.

New Features:
- Multiple bindings for each service
  Use comma-separated interfaces on Interface= lines in the ini file.
  Default is now "0.0.0.0,::"
- IPv6 support
- TLS support for the webserver and (non-static) services
  New TLS option in services.ini (ie: Options=TLS)
- Decrease LEN_SCAN_CMD to 35 chars, increase the CID field to 45 chars,
  and rename the MAIL_CMD string to IPADDR.  I think this frees up the
  note field for SysOp use.

clients, timeouts, etc.) into the various *srvr.h files and use them instead of
hard-coded constants sprinkled through-out the .c files.
If the web server "max_clients" key isn't specified in the sbbs.ini file,
use 0 (unlimited) for the max_clients value.

The connect timeout is now configurable in sbbs.ini [Mail] ConnectTimeout
(default = 30 seconds), set to 0 for blocking connections (and OS-default
timeout).

- if configured max recipients = 0 means unlimited (for all users)
- max recipients limit is applied to pending send emails (non-M-exempt users)
- M-restricted users can not receive unauthenticated SMTP mail messages
- Introduced inbox msg limit (for non-M-exempt users) with sbbs.ini [Mail]
  MaxMsgsWaiting value (default: 100), 0 = unlimited

The attempt list can be view with sbbscon->'a' command or sbbsctrl->view->Login
Attempt List...
Delay/throttle/hacklog/and auto-filter values/thresholds are now configurable
in sbbs.ini.

error counting/logging/messages to be handled by front-end (e.g. control panel)
regardless of log_level setting.
Mail server now filters blocked-subjects before applying DNSBL tag.
Received message header TO and FROM fields are no longer checked against the
email.can file for SMTP-authenticated clients.
SMTP MAIL FROM and RCTP TO addresses are no longer checked against the
email.can file for SMTP-authenticated clients.
Statistics are displayed in a more legible manner when the mail server is
terminated.
The msgs_received stats counter now includes blocked and ignored messages too.

Configurable via ctrl/sbbs.ini file JavaScriptLoadPath key value
(comma-separate listed of search directories), default value is "load".
This list is exposed in the JS object model via the js.load_path_list array
(may be modified by scripts).
For JSexec, the default load path list may be over-ridden with the '-i' option.
For relative load paths (e.g. not beginning with '/' or '\'), the path is
assumed to be a sub-directory of the (configurable) mods or exec directories
and is searched accordingly.
So, by default, load("somefile.js") will search in this order:
mods/load/somefile.js
exec/load/somefile.js
mods/somefile.js
exec/somefile.js