Takayuki Miyoshi

See Checkboxes, radio buttons, and menus

What is it? Where did you get it from?

What other plugins and theme do you use on the site?

See How to resolve configuration errors

See Adding a custom form-tag

Where can we see the website in question?

Where can we see the website in question?

What plugin do you use for the newsletter sign-ups?

Try switching to the default theme, deactivating all plugins excluding Contact Form 7 and WP Mail SMTP, and clearing all cache data.

Why you are advised to deactivate plugins and switch to the default theme.

You can set the fallback email using the wpcf7_mail_components filter hook. The warning in the Mail tab still appears, but you can ignore it as you know it’s not valid.

See Message body

Why don’t you simply put the whole <tr>...</tr> into a single line?

Shortcodes are not executed in a Contact Form 7 form.

OK. Update them first.

Yes, the format is correct.

The problem is that many people forget the basic rule that an ID must be unique in the whole document.

What message did you get?