On Monday, May 21 at 12:07 AM, quoth Samuel Murez:
The question to answer here is: where is the failure occurring? The
failure must lie in one of three places: either the program making
the query (dnsq) is broken, or the program doing the lookup
(djbdns) is broken, or the server you're asking for data is broken.
Since dnsq doesn't have logs, and we don't have access to
hotmail.com's DNS logs, I think it's fairly reasonable to assume
that I'm talking about the djbdns logs (i.e. the only dns logs that
you have access to). From there we may be able to figure out what's
going on. They may not help, but they're the best place to start.
Thanks for your answer. Sorry to be so slow, I haven't worked with
dns before.
Happy to help.
From what I can tell, I don't have djbdns correctly installed and
configured.
Yup, and probably a large part of that is that BIND is listening to
127.0.0.1:53, which is preventing djbdns from using that port.
It is my understanding that though it helps with the cname deferral
problem, it's not strictly necessary for qmail. Is this the case ?
Correct. I only started talking about djbdns since you said that you
had installed it.
Just to get a handle on my issue here (please correct me where I'm
wrong) :
my qmail is not sucessfully sending mail to many large mail servers
that we can presume are not all having problems at the same time.
the errors, can't establish an smtp connection, and cname deferral,
could both be due to a problem with dns lookups ?
No. The cname deferral is most likely a problem with DNS lookups. The
failure to establish smtp connection error you saw could be one of two
things: network problems, the recipient's server is down, or bad
domain info (on the part of the recipient). One thing that might cause
both is general network flakiness (e.g. if your router is dropping
lots of packets), but in general, they're separate problems that need
to be resolved separately.
this problem is happening now though it wasn't occuring before, during a
few years where my mail setup was working fine, and I made no
configuration changes.
Has *anything* about the box changed? Has anything about its
environment changed?
we're now trying to figure out what's happening during the dns lookups,
that work fine on the 2nd try from the command line.
Right.
Do you know if when a dns lookup is requested by qmail, it would be done
only once, or a second time if it fails ?
It is done once per connection attempt.
If qmail were to start second-guessing everything about the system,
one has to ask: why stop at two lookups (if the first one fails)? Why
not three? or five? or a hundred? At some point qmail has to assume
that the services it relies on are doing their jobs properly. And if
they're doing their jobs properly, asking once should be more than
sufficient to get the best possible answer at that time (i.e. a
failure means that the name cannot be looked up right now, and asking
a split-second later has no expectation of success).
~Kyle
--
Just because you do not take an interest in politics doesn't mean
politics won't take an interest in you.
-- Pericles (430 BC)
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