This error means a form tag that is not an email, dynamic_email, hidden, or dynamic_hidden form tag is being used as the value of the To or From fields or as values for the Cc, Bcc, or Reply-To headers.

To resolve, you need to update form tag that you’re using to select an email address to one of these form tags.

This configuration error extends Contact Form 7’s “Invalid mailbox syntax is used” error.

This error means a dynamic_hidden form tag that is being used as the value of the To or From fields or as values for the Cc, Bcc, or Reply-To headers is resulting as empty or blank. If this field is empty, it can cause an error in the mail-sending function on some hosts.

To resolve, you need to ensure that the default value always results in a valid email address by prepopulating the field with a static value or a dynamic value via shortcode, so long as it’s never empty.

This configuration error extends Contact Form 7’s “There is a possible empty field” error.

This error means a dynamic_email form tag that is being used as the value of the To or From fields or as values for the Cc, Bcc, or Reply-To headers is resulting as empty or blank. If this field is empty, it can cause an error in the mail-sending function on some hosts.

To resolve, you need to set the field as required OR ensure that the default value always results in a valid email address by prepopulating the field with a static value or a dynamic value via shortcode, so long as it’s never empty.

This configuration error extends Contact Form 7’s “There is a possible empty field” error.

This error means a dynamic_email or dynamic_hidden form tag that is being used as the value of the To or From fields or as values for the Cc, Bcc, or Reply-To headers is return a value that does not follow valid email address syntax, e.g. “[email protected]”. If this field is invalid, it can cause an error in the mail-sending function on some hosts.

To resolve, you need to ensure that the value always results in a valid email address that follows the appropriate email address syntax.

This configuration error extends Contact Form 7’s “Invalid mailbox syntax is used” error.

This error means a dynamic_email or dynamic_hidden form tag that is being used as the value of the From field is a valid email address, but it does not belong to your website’s domain. If your website sends the automated email from your web server but the email address says “[email protected]” (and your web server isn’t Google or Gmail), then there is a high risk that the relaying mail servers will identify your email as spam due to the spoofed email address. Identifying automated emails sent from your web server as such will reduce that risk.

To resolve, you need to ensure that the value always results in a valid email address that belongs to your website’s domain.

This configuration error extends Contact Form 7’s “Sender email address does not belong to the site domain” error.