> I will have the following:
>
> Computer A (On ISP Primary)
> | - Linked via 100Mbps ethernet
> Computer B (On ISP Secondary)
>
> I'd like to setup A as the first MX record for host blah.com and B as the
> secondary MX record for blah.com both on different ISPs and connected via
> 100Mbps ethernet.
>
> If A is down and B starts receiving email for A, how do I forward all the
> emails B receives to A over the ethernet and not keep copies of those emails
> on server B?
Hi,
This is straightforward, using control/locals, control/rcpthosts and optionally
control/smtproutes:
Your primary MX, "A" is where the mail is delivered, so put your domain in
control/locals
and control/rcpthosts. Your secondary MX, "B", where mail is not delivered, merely held
while "A" is unreachable, has your domain in control/rcpthosts but not control/locals
- so
that any mail accepted by this machine is not regarded as local and will be queued for
later remote delivery. Remote delivery will be attempted periodically by qmail (see the
man pages for details of this). You didn't mention if the 100MBps link was a public or
private link. If the latter, you need to add the private address of "A" to
control/smtproutes for your domain - this overrides the DNS entry for "A".
More details on all the above in the standard sources of documentation - start at
www.qmail.org, esp. see the man pages, Dan's site (cr.yp.to), Dave Sill's Life with
qmail
and the qmail howto.
cheers,
Andrew.
