Added support for optional MX records (add "-mx address" to dyndns cmdline).

the file transfer protocol is "Native 32-bit" (e.g. Nemesis Transfer Protocol).

Created strListAddAt() to add a string at a known index in the string list.

xpdev/ini_file and future modules that need to deal with string lists.

header incorrectly, which based on the query name, could result in a failed
MX-record look-up.
Added bounds-checking to queried name lengths.

to 40 chars.

chars following space.

msg-id", but "expand header fields".

(starting with white-space). Ex-ASCII chars could've been interpretted as
white-space.
parse_header_field() now supports "obsolete" header field syntax
(e.g. "from<white-space>:data").
The sender and sender_address fields (passed to external mail processors)
are now parsed from the received message header (if specified) over-riding
the SMTP "MAIL FROM" command "reverse-path" value.

A bit dated now.

repair of corrupted ptridx values (which will go away soon).

Display sub-board's internal codes when detecting duplicate ptridx values.

are specified, check the system.temp_dir.