[TYPO3] Problem turning of html mail format with powermail and typo3 4.2

[Mladen Babic]

I am still beginner in typo3,
and it is almost certain that I am doing something wrong.
But, i have problem turning of html format.
I tried unchecking "HTML format" in  constant
editor/plugin.powermail.additionalconfig,
and than get:
plugin.powermail.enable.html = 0    line in constants, but form is still
sending html emails with errors probably,
which also are bad rendered by gmail for example.

I don't know what i'm doing wrong, so i would appreciate any kind of help or
advice.

Thanks