How to limit spam emails received on the contact form
There are several ways to block spam on the contact form.
1. You could add a captcha field to the Contact Form 7 contact form:https://www.diigo.com/item/image/4ruxh/v5mi
To use CAPTCHA, you first need to install and activate Really Simple CAPTCHA plugin.
2. Another alternative(which I recommend, since it`s unobtrusive) would be to use the Contact Form 7 Honeypot plugin. It works on the same principle, but without forcing users to insert a captcha text.