Question : Email Blacklist

I have an email server that I use to host email for several companies.  Somebody must have sent something out or someone has a virus that flagged our server to be listed on a blacklist.

How can we combat this?  How can we make sure that people using our server does not get it blacklisted?  I certainly cannot be going around checking every PC from every company for viruses that uses my mail server.

Is there any sure way to prevent others behavior from flagging my server?

I have good policies setup that require authentication and my server is not an open relay.

Does anyone know of any good sites that check a large amount of blacklists?

Answer : Email Blacklist

Sounds more like one of your customers sent out broadcast email.  SPAM.

This is quite common.

Ways to prevent it are to limit the amount of email they are allowed to send.  Get better customers!

Some blacklists will give you the offending email, to track down what customer is at fault.