I am assuming you are using a form to submit feedback to eBay regarding the site, not feedback concerning a transaction -- correct me if I am wrong.
Email from eBay tends to be one way; you cannot reply back to most eBay email messages. In most cases the address has no inbox or incoming mail is dropped or ignored.
The email my include a disclaimer: "We don't check this mailbox, so please don't reply to this message."
If eBay is expecting a response from you, there is usually a button or a link to send a message instead of replying to the email directly.
