When Magpie could not sign in to its email service, marking a Store order as shipped saved the shipment and then showed an error. The shipment is now saved and the page finishes normally; the email that could not be sent is logged for the team that runs Magpie. The same applies to every other email Magpie sends.
Internal: the Store tests now give the order service a recording mailer, so they no longer try to send real email when an earlier test has set a sending address, and no test waits on AWS for credentials.