If you are load balancing rather than providing a "secondary" (backup) MX of
a lower priority, the only thing I would add to what Chris said is the
choice between publishing 2 MX's with the same priority, or a single MX
which points to a round-robin'ed pair of A records.
If you publish two MX's of the same priority, it is up to the sending side
to pick one "at random". However, there are quite a few broken MTA's out
there which will always use the first one in the list, so your load
balancing will tend to be skewed.
By publishing a single MX which points to a round-robin'ed pair of A records
(i.e. two A records with the same hostname but different IP's), then you
control the load balancing, rather than the remote MTA's, and you usually
find that the balancing is more even.
The down side of using the round robin A record is that if one of them dies
and you have to take it out of the rotation while you fix it, remote MTA's
won't pick up on the other one till the TTL for that record expires.
-- hugh
> -----Original Message-----
> From: Chris Gebhardt - VIRTBIZ Internet [mailto:cobaltfacts (at mark) virtbiz.com]
> Sent: Wednesday, July 11, 2007 5:14 PM
> To: coba-e (at mark) bluequartz.org
> Subject: [coba-e:10378] Re: more than 1 mx record or not
>
> Steffan wrote:
> > Hello List,
> >
> > Just wondering.
> > im using grey listing etc
> > And using 2 mail servers for my clients domains
> > But reading on Internet I see more posts that say that today the day
> > Is is better not to use more than one mx record for a domain
> > But just use one mx record
> > When this is down the mail bounces back but the server will try again
> later
> >
> > Im just wondering what the ideas of the experts are in the list :-)
> > Do you stil need today more then one mx record for a domain ?
>
> From what I have seen, this advice is given because the author assumes
> that the spam filtering on the "secondary" will be less effective than
> what is on the "primary" MX.
>
> In my experience, there are many spammers that will intentionally ignore
> the MX preference, or actually use the lower preferenced MX to send mail
> to a domain. The thought process is that the spam filtering may get
> bypassed in this way.
>
> We run 2 MX relays for all of our virtual hosting customers. They are 2
> separate systems in 2 different datacenters and 2 different networks.
> Both servers run the same filtering rules, and sync themselves every
> hour. So no matter which MX is used, the filtering is the same. If
> something ever happens to one of the MX's, the other is standing by, and
> there is NEVER a bounce or a delay.
>
> Everybody has their own opinion, but obviously, my company feels that 2
> MX's with identical configurations is preferable to a single point of
> failure.
>
> However, if you were in a situation where your primary MX was the spam
> filtering system and the secondary was not filtered, then go with the
> single MX and save yourself and your customers from the spam.
>
> --
> Chris Gebhardt
> VIRTBIZ Internet Services
> Hosting, Collocation, Dedicated Servers, Internet Access
> (972) 485-4125 | http://www.virtbiz.com