Hi there @thepowerofcopy, 

Thanks for making us aware of this interesting scenario! 

Yes, this is likely a Amazon/Codisto domain. As such, I would recommend creating a segment to gather these users to prevent them from receiving your sends and suppressing them  in order to not hurt your deliverability. 

Thanks for participating in the Community!

-Taylor 

Codisto is an integration app for third party marketplaces (eBay, Amazon, ETSY etc) that integrates, maps and sync’s products from your web site to those sales channels.

Now, those sales channels don’t like sellers getting access to contact information or email addresses of customers, so they block this information from being viewed on their seller portal. Codisto are also forced to sync/show an alias email address back to your web site, which then shows in your web site database and Klaviyo as an alias.

There are some exceptions. If the sale is to an international customer, you usually will see the customers email address if you are viewing their delivery information but only before you mark it as Delivery Sent/Completed. Once sent they will mask the email address or hide it. If you purchase international shipping label/doc on the third party sales channel (eg. eBay) I know that the purchase shipping labels will contain the email address. But if it’s local/national customer (same country) then you won’t see their email address at all.

If it’s an international customer then you can always manually update your web site or Klaviyo from the shipping information.

Hope this helps someone with the same question.