We don't yet support UTF-8 in node/user messages.

(ctrl/node.dab) is constantly closed and re-opened for every non-locking read.
This is really slow across network file systems and unnecessary, so use a
similar optimization as the C++ sbbs_t class where the file can (and normally
is) left open across multiple consecutive reads.
Create/use opennodedat() function.
Uses the new CLOSE_OPEN_FILE() macro from xpdev/filewrap.h.

is being forwarded to an external email address. Introduced in rev 1.690,
user-forwarded emails wouldn't work because sending envelope would contain
the original forward-path. Thanks again to Alterego (ALTERANT) for testing
this stuff and reporting issues with detail!

when decoding. Linear-white-space between regular atoms or between atoms
and encoded words is retained (as a single space character, Yoda).

Advertise STARTTLS support (in EHLO response) when *not* already using a TLS
connection.

pointer type mismatch in conditional expression
format '%s' expects argument of type 'char *', but argument 5 has type 'void *'

MIME-encoded.
If any RFC822* header field is a MIME-encoded UTF-8 string, then set the
(new) auxattr MSG_HFIELDS_UTF8 flag. This will be used (soon, hopefully) to
display UTF-8 encoded header fields to users. There's a gotchas here:
- MIME-encoded header fields with other non-ASCII/8-bit charsets (e.g. CP437,
  ISO-8859) are still stored "as decoded", though the MSG_HFIELDS_UTF8 flag
  may be set *later* (which would be weird), resulting in a mixture of valid
  and invalid UTF-8 header fields. One solution would be to UTF-8-transcode all
  the non-UTF-8 header fields if *any* of them are UTF-8, but we wouldn't
  know which charset to translate *from*. Assuming CP437 isn't going to be
  correct 100% of the time - so punt for now and deal with it at display
  time. e.g. if the MSG_HFIELD_UTF8 auxattr flag is set, but an hfield contains
  invalid UTF-8 data, don't display as UTF-8 (e.g. treat as CP437). We don't
  have translations for other charsets (e.g. ISO-8859) setup yet anyway.

(e.g. for UTF-8 Fido or QWK netmail messages sent over SMTP or POP3).

New function (derived from sbbs_t::utf8_to_cp437()): unicode_to_cp437()
New utf8 functions: utf8_replace_chars(), utf8_str_is_valid().
utf8_getc() enhancement: val arg may be NULL (for length/validation uses).

Convert quoted UTF-8 message text to CP437 when terminal is not UTF8.

Set Fido CHRS: UTF-8 header field when posted message is UTF-8.

chars) so that massize MIME encoded header fields can be parsed successfull. :-|

MIME-encoded headers.

getting kind of crazy common now and being employed even when totally
unnecessary (e.g. encoding strings that contain just plain ASCII):
- normalize message header fields, when possible
- normalize UTF-8 encoded characters, when possible (e.g. special punctuation
  chars)

This allows text filters (e.g. subject.can, name.can) to work on MIME-encoded
header fields and notifications about received e-mails are legible to humans.

Encoded-words that contain actual non-ASCII/CP437 chars (e.g. foreign symbols,
emojis) are left as encoded-words to be dealt with by whatever displays the
message header.

Special handling of folded normalized field values was necessary because
"White space between adjacent 'encoded-word's is not displayed." (per RFC 2047)

resolved host-name on "Hostname:" log lines.

We don't store (findable) hostnames in the file, so don't search for them.
Don't search file if the host is listed in the spamblock_exempt.cfg file.
If you have a really large spamblock.cfg file, this could result in the
unnecessary reading of potential many megabytes of data for each inbound
SMTP connection. We might want to read this file even less frequently and
store the list in a searchable str_list_t or something.

smb_freemsgmem():
bounce() is using a strange method of copying a message header in memory
(not using smb_copymsgmem) and when it frees the message, ends up with a
double-free of the 2 new smbmsg_t members (not header fields): text_subtype
and text_charset.

after sending via POP3 (the MSG_READ attribute flag is already indicating that).

headers).
Don't reference the (currently unused) times_downloaded and last_downloaded
msghdr_t elements/properties.
Set the current node action value *before* calling the scanposts_mod
("Scan Msgs module") in sbbs_t::scanposts().

angle brackets in the "RCPT TO" command sent to the SMTP server. This is an old
bug but now appears because we are now (recently) actually storing the SMTP
forward-path in the message header.

headers

- getnameinfo() was being called with NI_NUMERICHOST in the mail server and
  web server (but nowhere else)
- use a singly-defined macro (STR_NO_HOSTNAME) for the "<no name>" string
  rather than copying it about
- the webserver apparently assumes that session->host_name will always have
  *some* unique value (e.g. the IP address when no hostname is available) - so
  account for that special need <grumble>

MIME-encoded/embedded attachments.
We probably will want to do this for SMTP-posted messages (to subs) too.

strrchr() here to find terminating chars (quotes, parens, brackets).
e.g. '"Joe Shmoe" <joe@shmoe.com>, "Fred Smith" <fred@smith.org>'
would be parsed as 'Joe Shmoe" <joe@shmoe.com>, "Fred Smith'.

back in 1993, but were never needed/used.

to a second thread before the first has the session set active.  Add calls
to lock/unlock the certificate to prevent this.

The better options is likely to have a function that adds the key and socket
and sets the session active in one call and handles the locking internally.

But I'm lazy, so we get the lock functions.

(JS bbs.post_msg()): If the WM_QUOTE mode flag is *not* set, then it will auto-
create the quote file (quotes.txt) and add the WM_QUOTE mode bit before calling
sbbs_t::writemsg(). So if existing JS scripts call bbs.post_msg(..., WM_QUOTE)
with a custom-created quote file (e.g. with msg tails), that'll still work as
before (e.g. DDMsgReader.js).

bbs.email() and bbs.netmail() now support an optional reply_header_object
argument which works like bbs.post_msg(). These methods (and the underlying
C++ methods: sbbs_t::email(), netmail(), inetmail(), all auto-create the
quote file now, when the WM_QUOTE mode flag is *not* set.

The auto-created quotes.txt now includes the plain-text version of MIME-encoded
messages.

the bbs.post_msg(), email(), and netmail() methods now all support reply
header objects that came directly from bbs.get_msg_header() *or* copies of
such header objects (but the auto-quoting feature won't work when supplied
this type of header object). So if passed a header object returned from
bbs.get_msg_header(), we can now use the message base (for auto-quoting) and
the underlying msg storage directly (no JS parsing necessary). This is what
the new js_GetMsgHeaderObjectPrivates() function is used for.

js_ParseMsgHeaderObject() (and the underlying parse_header_object() function)
now supports either an actual internally-generated msg header object (e.g.
returned from bbs.get_msg_header()) or one that is a copy or hand-constructed.

quotemsg() no longer tries to get a copy of the msg index/header. It shouldn't
have to since we can now get to underlying msg storage in the js_msgbase.c
via js_GetMsgHeaderObjectPrivates().

quotemsg() now reads only the plain-text portion of MIME-encoded messages.

As part of this effort, I modernized the method prototypes using default
argument values (e.g. WM_NONE for wm_mode arguments) and removed some
extraneous WM_EMAIL and WM_NETMAIL specifications (these wm_mode flags are
automatically added by the sbbs_t::email() and *netmail() functions).

savemsg() now *does* support reply-IDs/thread-linkage via the additional
'remsg' argument (when non-NULL).

Replaced some use of nulstr with NULL.

Replaced more boilerplate SMB open code with calls to smb_open_sub().

251 response which was made optional in RFC2821 - to address privacy
concerns.

- include errno description (strerror output)
- exclude (redundant) node number

to warning - this is normal/expected (e.g. when mail base is being
backed-up).

mail "To" and "From" header fields of the form: user name <user@addr> or
"user name" <user@addr> - the email.can filtering would not work

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).