I've been using them for the past 2 years and never had a problem, though it did seem to work a lot happier using OE6 than other mail clients like thunderbird. Using Netscape 7's mail program it constantly kept asking for my password and failing to log on. They were sods when I tried to cancel a domain they were hosting. They denied all knowledge of receiving my cancellation notification. I faxed it to them in the end.
I would imagine a virus on the mail server would make life interesting but I'm surprised they can blame the users. If that's the case then email servers should never be working. Poor excuse I think.