On Sat, Mar 12, 2011 at 07:19:08AM -0600, Stan Hoeppner wrote:
> Wietse Venema put forth on 3/11/2011 8:55 PM:
> > Stan Hoeppner:
> >> I've often wondered why MX lookups aren't disabled
> >> automatically when setting relayhost=.
> >
> > Because there is no way to turn it on! A feature that can't
> > be turned off is a bug.
> >
> > Wietse
>
> Maybe I asked my question in the wrong way Wietse. What I'm
> wondering is how doing MX lookups is ever useful when relayhost
> is set. I don't see how it could be.
I have simplified since then, but at one time I had two relayhosts
that I'd use from home. One was/is the primary, but there were
problems sometimes, when the primary was down.
So I used "relayhost = relayhost.my.vpn":
relayhost.my.vpn. MX 10 primary.relayhost.my.vpn.
relayhost.my.vpn. MX 20 secondary.relayhost.my.vpn.
So, outbound mail would move even if the primary relayhost was
unreachable or down.
> If it's never useful when relayhost is set, then it makes sense
> to me to automatically disable it when relayhost is set.
> Obviously I lack understanding of MX lookups in relation to
> relayhost. Please explain how to the two interact.
It's a feature, if you choose to use it. There's nothing special
about relayhost per se, but it makes sense to me that MX records
should govern mail routing.
Regarding the original question in this thread, I would have
recommended MX records of equal priority, and not CNAMEs. This
doesn't seem like a necessary use for a CNAME.
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