Vote for ActivatorMail
ActivatorMail may be used as a frontline filter system for any standard email server such as Microsoft Exchange, Unix/Linux SendMail, or Lotus Notes. All that is required is to set your domain's DNS 'MX' (mail service) records to use ActivatorMail services. This simple change can be done by your Network Administrator or ISP and directs email addressed to you to ActivatorMail first. Then, only 'Clean' email is delivered to your mail server. You simply continue to use your own mail server with all its Internet email filtered automatically by ActivatorMail.