How To Use GMail for Corporate Email Filtering (Free)

GMail overall has a nice spam filter. You can leverage the GMail spam filtering capability even for your corporate emails without paying a dime.

First create a free GMail account if you do not have one already.

Configure your corporate email account to forward all your emails to your free GMail account. For Linux based mail servers like sendmail or Postfix all this means is that you create a .forward file in your home directory with the GMail email address you want to forward all your emails to. For Microsoft Exchange based servers, it is probably easier to configure your email client to forward all your emails to your GMail email account.

In Gmail settings configure it to allow access via POP3.

Now configure your email client (Outlook, Outlook Express, Evolution, Thunderbird etc.) to fetch your emails from your GMail account (instructions).

To send emails, configure your email client to directly use your corporate mail server.