On 26 Nov 1997, Newsgate wrote:
> When Exim tries to send mail to remote host, it checks availability of this
> host, of cource :-) If deliver to this host is possible, it try to do this.
> If there are errors, exim stop transfer up to next retry time. It is correct.
>
> But what exim must to do, if lookup of this host is unsuccessfull? Must it
> comply to this mails the same retry rules? Can I say to exim: try to lookup
> hosts 4 hours and then, if unsuccessfull, drop this mail and return error
> to sender?
>
> In most cases unsuccessfull host's lookup means unexistent host and don't need
> delivering at all. IMHO ;)
If the host does not exist (i.e. the DNS says "no such host"), Exim
immediately fails, and returns the message to the sender.
If the host lookup does not complete, Exim waits and tries again later.
This can happen if the DNS server for the domain is broken or its
network connection is down. Retrying the lookup is controlled by the
retry rules. From the manual:
Retry processing applies to directing and routing as well as to delivering.
...
When looking for a retry rule for a remote delivery, each line in the retry
configuration is first tested against the remote host name, and then
against the address's domain name.
If it hasn't got as far as looking up up a host, then it just matches on
the domain name. As there is a timeout_DNS error recognized by the retry
rules, you could specify a retry rule for certain (or all) domains that
gave up more quickly after a DNS timeout, e.g.
* timeout_DNS F,4h,15m
--
Philip Hazel University Computing Service,
ph10@??? New Museums Site, Cambridge CB2 3QG,
P.Hazel@??? England. Phone: +44 1223 334714
--
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http://www.exim.org/ ***
