On Mon, 22 Aug 2005 08:46:59 PDT, SM said:
That A record MUST point to the SMTP Client.
And the IP address of the SMTP client MUST resolve back to the hostname.
That may not be possible with multi-homing.
out-mail.example1.com A 192.168.0.10
out-mail.example2.com A 192.168.0.10
10.0.168.192.in-addr.arpa PTR out-mail.example1.com
10.5.0.10.in-addr.arpa PTR out-mail.example1.com
18.104.22.168.in-addr.arpa PTR out-mail.example2.com
It's *possible* to set it up. The biggest problems you hit are:
1) A *lot* of software doesn't understand that PTR records can be multi-valued.
2) An even more incredibly large number of sites don't do DNS-over-TCP or EDNS0,
so if the list of PTRs ends up over 512 bytes, things go pear-shaped quickly.
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