Contact Form 7 provides Configuration Validator, which validates your contact form configurations to detect errors; this saves you from future troubles that the configuration errors might bring on. This series of articles explains common mistakes and how to resolve those errors.
General information and an introduction to the Configuration Validator are explained in FAQ about Configuration Validator.
Errors in the Form Tab
- Unavailable names are used for form controls.
- Multiple form controls are in a single label element.
- Unavailable HTML elements are used in the form template.
Errors in the Mail Tab
- There is a possible empty field.
- Invalid mailbox syntax is used.
- Sender email address does not belong to the site domain.
- There are invalid mail header fields.
- Attachment file does not exist.
- It is not allowed to use files outside the wp-content directory.
- The total size of attachment files is too large.