Apparently developers at Transa (a Swiss outdoor supplier) can't be bothered to read RFCs. Translation of the red box: "This does not look like a real email address". Well, as RFC 3692 nicely describes this does in fact look like a valid email address. But yeah, why research how to validate an email addresses. It's way cooler to invent your own rules.
#^RFC 3696: Application Techniques for Checking and Transformation of Names