[Lorenz-Kraft]

If your reputation is good enough or if you manually whitelisted nagios/munin/etc. messages, your don't get any problems. Its mainly a problem for new mail server setups (new domain). Bye the way "whitelisting" in Outlook takes some time. But after that, you should not have any problems with Outlook.

[feanaro]

This is what I thought too, but my domain is not that new anymore and things seem to be getting worse. I know all the users personally so I know none of them ever sent any spam so that shouldn't be a problem either.