New behaviour on 5.0.9 was to replace leading white space (spaces) in text lines with notes margins which broke many processes that relied on leading white space formatting in lines. This parameter, when enabled, reverts to the old behaviour of leaving it alone.
This setting was introduced in 5.0.10
This vartiable is new in 6.5.4
SPR# HKAI636AXA - Fixed a CR LF detection problem where the wrong character was inserted in the last line if the Notes.ini "MIME_KEEP_TEXT_PLAIN_FORMAT=1" was used.
This regression was introduced in 6.5.2.