On Wed, Mar 01, 2006 at 11:16:59PM -0600, Graham Toal wrote: > Personally I do believe in Backup MX, as long as it does proper > relay checking. It's nice if it also does spam checking, but > not critical because your primary MX will still do that. However > if you do spam checking *and rejection* on your backup MX, you'll > significantly lower the load on the primary when it returns.
multiple prioritized MX is fine, as long as they're under the same administrative control with similar settings. "Backup MX" to me means some other site that just takes any mail for your domain and blindly forwards it on. I ran it for years. I've had other people run it for me. It's a disaster. In the modern world of spammers and smtp, any mail you have to generate a bounce message for (i.e. your relayhost accepts a mail for an invalid account on your primary host) means either someone else is getting junk from you or the backup host has to deal with double bounces. I prefer to avoid the junk.
