ShipScript has been an eBay Community volunteer since 2003, specializing in HTML, CSS, Scripts, Photos, Active Content, Technical Solutions, and online Seller Tools.
When you receive a message from another member, that other member's email is shown as an eBay alias so that you will not have access to their true email. Likewise, when you send a message, that other member will see only an alias. You would never see your own alias.
Additionally, FedEx can not send a message to that alias. I've tested, and it is not possible for a person outside of the email conversation to send to an alias@members.ebay.com.
However, if you are the buyer and FedEx wants to confirm the email alias sent to the carrier matches your alias, you could message the seller to ask what email they used on the documentation. Otherwise, tell FedEx that the @members.ebay.com is internal to eBay and non-functional outside of eBay. Give them an actual email if they need to send you something.
