I don't see the emails from the list.

[Jay R. Ashworth]

On Sat, Sep 29, 2007 at 06:40:35PM -0700, Bill Campbell wrote:
> On Sat, Sep 29, 2007, Jay R. Ashworth wrote:
> >On Sat, Sep 29, 2007 at 06:18:00PM -0700, Bill Campbell wrote:
> >> Our largest regional ISP customer only lists a single MX server
> >> which handles all their incoming mail.  If there's a problem with
> >> that machine, we can change the DNS to have it go to another
> >> server in minutes.
> >
> >DNS caching client-ISP-side doesn't cause you problems there?
> 
> Not that I've ever noticed.  We're running djbdns' dnscache on the machine.
> We use very aggressive DNSRBLs *AFTER* first checking an extensive DNSRBL
> white list.  Since postfix doesn't support DNSRBL whitelisting, I've
> enabled the tcp dictionary, and written a little tcp server in python that
> handles this, caching lookups as the whitelists change very slowly.

I wasn't clear: you're talking about public-to-the-Internet MX records.

If you change the MX record in DNS, unless you commonly run it with a
wildly low TTL, people in teh outside world will lose the ability to
get mail *in*, no?  And remember: some ISP caching servers are reputed
to *ignore* low TTLs, rewriting them up.

Cheers,
-- jra
-- 
Jay R. Ashworth                   Baylink                      jra at baylink.com
Designer                     The Things I Think                       RFC 2100
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