[HLUG] Exim 4.50 on Debian 3.1 external greet_pause?

[John Hedges]

Hi Mark
 
> On 29/01/07, John Hedges <john at drystone.co.uk> wrote:
> >On Mon, Jan 29, 2007 at 04:01:44PM +0000, Mark Broadbent wrote:
> >> [...]
> >
> >Thanks Mark. Maybe I am less than bomb-proof. However I'm still not
> >convinced that the (im)probability of receiving mail from a broken
> >sender when your primary is down warrants maintenance of a second mail
> >server. Perhaps it's a bit hard line but it's better not to pander to
> >broken/misconfigured senders. You never know, it might prompt them to
> >get their servers fixed :) And as far as the warning messages are
> >concerned, aren't they useful to the sender?
> 
> I greatly depends on your circumstances, for me, my primary is located
> in my house and is off most of the time so I want the backup to
> collect mail and hold it quietly for upto 2 weeks (like when I go on
> holiday).  For a business who relies on email then you have no option
> but to make it as easy and bombproof as possible for your customers to
> send you email.  But for everyone else, it won't matter.
> 
> >If your secondary can deliver mail, then fine - it's obviously useful in
> >that you are improving availability, but just to spool seems pointless
> >to me.
> 
> Very rarely would a secondary actually deliver mail (as I said before
> it would be a redundant primary if it did)

That's exactly my take on the provision of a secondary MX, to be a
redundant MX for when the primary fails. I'm sure that many ISPs will
use mirrored SMTP relays as secondaries that will do full mail
delivery. Your situation is different because you are dealing with a
mailserver that handles local deliveries.

> it's a good way of
> reducing the delivery delay for email that was delivered whilst you
> were off-line. Depending how long the primary is off-line, it could
> take 1-2 days to actually receive all the stored email when relying on
> the sending server to retransmit.  Again this highly depends on the
> sending servers configuration.
>
> Basically what I'm getting at is that it a defensive set-up to guard
> against other peoples mistakes.

Your configuration is interesting in that you are leveraging the
secondary MX as a mail queue. In many ways, I prefer it to mine which is
a primary MX on a permanently connected VM with mailboxes and either
IMAP direct to that host, or fetchmail for distribution into mailboxes
on a lan server. Either way, I rely on some sort of polling with IMAP or
POP3. However, you have two sets of ACLs to keep in sync and the
necessity to route inbound SMTP through your firewall.

Why don't you make your secondary MX your primary? It would always spool
when it couldn't forward to your home and you'd only need one set of
ACLs (plus a very simple one on your home server to allow SMTP only from
your mail server and lan). This would give you the same functionality,
would make more sense primary/secondary-wise and would allow you to
tighten your firewall.

Cheers

John