Configure sendmail to reject mail for unknown users?

[Gordon Messmer]

Timothy Alberts wrote:
> 
> Yes, it is 'msiscales.com'. The second MX record is supposed to be a
> backup when our server is down.

The suggestion that you use a virtusertable on your backup MX is a good 
one.  I do something similar at my site, where our mail filters run on 
top of sendmail, and are separate from the actual spooling servers.

Another option that I haven't seen mentioned is this: Don't run a backup 
MX.  Pretty much every sender will retry delivery on a reasonable 
schedule if your host is down.  I can't think of a single reason to run 
a backup MX at all.  They usually just create administrative overhead 
because of exactly the problem you're having now.