Cannot filter on envelope-to header
cPanel email filters cannot reference or filter on the Envelope-To header. In Exim (the mail transfer agent used by cPanel), the Envelope-To header is added by the transport at delivery time — it does not exist when filters are evaluated.
Workaround
Section titled “Workaround”The recipient from Envelope-To should also appear in the standard To or Delivered-To headers of the email message. You can create your filter rules using those headers instead.