Yes, one MX (with one name and proper PTR), and don't forget SPF records. As crappy as SPF is, it's expected in these times...
Cheers, Hans-Martin Am 3. Mai 2026 06:48:49 schrieb Viktor Dukhovni via mailop <[email protected]>: > On Sun, May 03, 2026 at 02:11:32AM +0000, Miles Fidelman via mailop wrote: > >> I'm busily migrating an old server to a new one, and in the process >> losing a bunch of IP address ... so now I'll be sending mail for >> multiple domains out of the same IP address. >> >> It's been a while, and what with DKIM & DMARC and all, I've lost track >> of the details. So I wonder if someone might offer some quick advice >> on configuring one server as the outgoing server for multiple domains, >> all behind a single IP. >> >> Specifically, since I need to set up a PTR to point to the server, any >> suggestions on how to set up the DNS records for other outgoing >> domains - so that DMARC works properly? > > There simplest, most natural approach is: > > ; MX host > ; > $ORIGIN host.example. > some IN A 192.0.2.1 > some IN AAAA 2001:db8::1 > ; > $ORIGIN 192.in-addr.arpa. > 1 IN PTR some.host.example. > ; > $ORIGIN 0.0.0.0.0.0.0.0.8.b.d.0.1.0.0.2.ip6.arpa. > 1.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0 IN PTR some.host.example. > > ; MX-hosted domains > ; > foo.example. IN MX 0 some.host.example. > bar.example. IN MX 0 some.host.example. > baz.example. IN MX 0 some.host.example. > ... > > -- > Viktor. 🇺🇦 Слава Україні! > _______________________________________________ > mailop mailing list > [email protected] > https://list.mailop.org/listinfo/mailop
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