check for email fqdn

cmd/welcome/main.go

@@ -93,7 +93,11 @@ func promptEmail(defaultEmail string) (email string, err error) {
 			email := val.(string)
 			_, err := mail.ParseAddress(email)
 			if err != nil {
-				return fmt.Errorf("could not understand that email: %w", err)
+				return fmt.Errorf("'%s' doesn't look like an email: %w", email, err)
+			}
+
+			if !strings.Contains(email, ".") {
+				return fmt.Errorf("'%s' doesn't look like an email: domain not fully qualified", email)
 			}
 
 			return nil