Is Hotmail in the habit of ignoring MX records?

One of my users has reported incoming mail failures, which I finally tracked down. It turned out that Hotmail has seen fit to send the mail to his domain's A record machine, despite the fact that he has valid MX records. The A record points to my webserver, which does not normally accept mail for anyone. The mail server MX records are to an entirely different machine. Comments? Do I need more valium? -=[L]=- --