@franklin82, @Van Halen and @jon6565,

this will be fix on the next release for the mean time change line 414 from

		$message = apply_filters( 'ims_email_headers', $headers, $ImStore->opts['tags'], $this->substitutions );

to

		$headers = apply_filters( 'ims_email_headers', $headers, $ImStore->opts['tags'], $this->substitutions );