Are there any reserved or unavailable words for the name of an input field?

Yes, there are some words that are not available; but this is actually not a restriction of Contact Form 7, but a restriction of WordPress.

If you post an input field with a name that is the same as a parameter name already used in a WordPress query, WordPress will confuse them, so you can’t use that name.

For example, ‘name’ is used in the query, so ‘name’ is not available for a field name. The best practice in avoiding unavailable names is adding a prefix or suffix to the name, for example, use ‘your-name’ or ‘name-1234’ instead of ‘name’.

See also: My contact form always redirects to 404 error page after submission.

Just another contact form plugin for WordPress. Simple but flexible.