On Wed, Jan 08, 2014 at 05:31:37PM -0500, Wietse Venema wrote:
> Postfix already has a feature that substitutes remote SMTP server
> replies (smtp_reply_filter).
>
> Maybe it's possible to implement a similar substitution for DNS
> server responses. If we want to use a regexp-based approach that
> requires a conversion from DNS reply to text. The text is then
> transformed by the filter, and then converted back to DNS response.
>
> I'm not recommending we do DNS -> XML + XPATH -> DNS.
I'd prefer to not go there at this time. The OP can put the hostname
in question into /etc/hosts, and update that via periodic DNS
lookups (which are NOPs when they fail). Then use a transport with
smtp_host_lookup=native.
This would work quite well if the C-library supports multiple A
records for the same name in /etc/hosts as with say various
Linux systems that have:
$ cat /etc/host.conf
multi on
An hourly cron job can keep the hosts entries for the fragile CNAME
up to date.
--
Viktor.
