Forum notifications are increasingly seen as spam, as they contain several links and as forum notifications are not that common these days anymore. So they might be blocked by email providers spam filters and not even end up in your spam box, so don't trust you will updated if you subscribed to topic updates or PM's for example. And it's way more fun to check back here more often
There are also reports of messages being sent from the bmwe21.net domain with a zip file attached. We can guarantee that we have nothing to do with that, virus spreaders using every popular domain or email addy to come across as a trusted sender. But attachments like .zip, .exe and the likes are always suspicious, I personally never open them.