Re: backup MX need (was Re: Hardware...)

[Seth Mattinen <sethm@rollernet.us>]

Andy Smith wrote:
> On Tue, Apr 04, 2006 at 10:52:54AM -0400, Dan MacNeil wrote:
> > Craig Sanders wrote:
> > [backscatter hellhole snipped]
> > > 99.9999% of the time your customers only THINK they need a backup
> > > MX (mostly because they're relying on obsolete advice from over a
> > > decade ago when backup MX servers weren't such a bad idea). these
> > > days they are rarely needed, and generally cause a lot more
> > > trouble than they are worth.
> > I'd be curious as to any details on how things had changed in the past 
> > 10 years.
>
> The internet got more reliable, the spam problem exploded, and
> having a server which accepts mail for *@domain and then bounces it
> later if the user proves not to exist became a serious liability.
>
> They only make sense if all MX servers know the valid users at each
> domain they accept mail for, and if they all apply the same
> antispam/virus measures.

Backup MX servers are quite handy if your primary system goes 
unavailable for any reason, and you want to catch up on all your mail 
right away, not when everybody else's mail server decides to retry. Keep 
in mind that there are still mail servers out there that only try once; 
two I've seen act like this are eBay and Southwest Airlines.

MX that doesn't filter and/or just accepts for anything@domain, yeah, 
they're part of the backscatter problem. But I wouldn't call secondary 
MX (as well as secondary DNS) useless. Properly done, it's still valid.

--
sethm@rollernet.us
Ne cede malis sed contra audentior ito