use squared brackets in email

Hi! There is any way to use squared brackets in email?

I have a select box named “category” with “info” and “order” and the subject field named “your-subject”.

In the configuration file I set mail subject like this:
category [your-subject]

So, I expect that when someone fills the form with “info” and “hello” to get an email with this subject:
[info] hello
instead I get:
[category] hello

There is any way to avoid this? I already tried to put the html char codes for squared brackets, but nothing…

Thanks!

http://wordpress.org/plugins/contact-form-7/