Valid values are:
0 - on (the user cannot send in both formats)
1 - off
Fixed in 6.5.1 - SPR# BCOE5LXQQA - The UI "sending message in both plain text and html format" will be disabled when the iNotes_WA_DisableBothFormats Notes.ini variable is set to "1".
This vartiable is new in 6.5.4
SPR# ASUH65FCGM - This fix provides a user with a means to re-enable the "both plain text and html" option, etc. for DWA language versions, disabling that by default.
This can be done by setting iNotes_WA_DisableBothFormats=0 to notes.ini.