[Plugin: WordPress Form Manager] Email validation not working

Hello,

I am using WordPress form manager for long time. And I love it.

But recently for some reason I got lots of spam email.
I found my subscribe email validation is not working. However, it works on another form(e.g contact form).

For my subscribe email form I removed the submit button and use Enter Key to let people subscribe. It that cause problem?

I’ve updated WordPress form manager to the newest version, but it still doesn’t work.

http://ww.wp.xz.cn/extend/plugins/wordpress-form-manager/