Fields appear to be highlighted

The fields on my form appear to have different backgrounds and the email field is outlined more so that the others.

Is there a way to stop this so that all fields are the same? The email is not the most important bit of information that we are asking for, but looks like it is due the outline.

Not sure if this is the plug-in or styling on the Theme (that I don’t have access to.

You can see it on the link below if you click the “Book Your Free Survey” button;

http://www.englishfireplaces.co.uk/products-page/fire-surrounds-by-material/marble/acanthus-m/

Thanks in advance.

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