12 Feb
2012
12 Feb
'12
1:38 a.m.
Hello,
On Sun, Feb 12, 2012 at 01:37, Mathew Newton
<bitfolklist(a)newtonnet.co.uk> wrote:
I don't believe such behaviour is particularly
widespread, and hence I
would be reluctant to rely upon it in practice. Indeed, RFC2182 is quite
clear on the importance of having reachable DNS even if the referenced
services are affected by the same issue(s) (e.g. if sat on the same box):
For SMTP specifically, the current specification is also quite clear
(RFC 5321, section 5.1):
"The lookup first attempts to locate an MX record associated with
the name. If a CNAME record is found, the resulting name is processed
as if it were the initial name. If a non-existent domain error is
returned, this situation MUST be reported as an error. If a temporary
error is returned, the message MUST be queued and retried later (see
Section 4.5.4.1)."
Earlier specifications were less clear, but this has always been the
common behaviour.
Regards,
Daniel