Question about virus/spam filtering for customers with mail servers

Scott Blaydes sblaydes at
Mon Jul 26 13:36:13 PDT 2004

Richard Kuhns wrote:
> I'm hoping someone will be willing to share a better way to handle this.
> We offer virus/spam filtering for customers with their own mail servers. 
> We're currently implementing this by configuring the customer's firewall 
> to only accept smtp connections from our servers (all running sendmail 
> under FreeBSD 4), and the customer's MX records point to their server 
> first and our server(s) second and third. In most cases this works just 
> fine -- attempts by a mail server to deliver mail directly to the 
> customer fail, the mail server tries the secondary MX site (us), we 
> accept and filter the message and deliver it to the customer (or not).

You could set up your FreeBSD boxes that are doing the 
scanning/filtering to be the primary and secondary MX for the domain and 
  then use sendmail's mailertable to deliever the messages to the 
customers' servers.  The mailertable will even let you ignore MX 
settings for the domain.

Scott Blaydes

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