Re: [Exim] [exim 3.31] strange retry behavior

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Auteur: Philip Hazel
Datum:  
Aan: Marc Haber
CC: exim-users
Onderwerp: Re: [Exim] [exim 3.31] strange retry behavior
On Mon, 29 Jul 2002, Marc Haber wrote:

> >Exim does not queue emails for 5 days[*]. It queues emails until a host has
> >been down for 5 days[*]. This is not the same thing.
>
> So if I have a domain
>
> domain1.example.com IN MX 10 mx.domain2.example.com
>
> and my exim has retry settings both for domain1.example.com and
> mx.domain2.example.com, the setting for mx.domain2.example.com will be
> used for mail to localpart@????


The setting for mx.domain2.example.com will be used for host failures
when delivering to the host mx.domain2.example.com, for any domain. (In
other words, "yes, for that particular host".)

Suppose there is a second MX record

domain1.example.com IN MX 20 mx2.domain2.example.com

Exim will go on to try that. If it also fails, Exim will look for a
retry rule for mx2.domain2.example.com. If it can't find one, it will
then use the retry rule for domain1.example.com.

In other words, if Exim suffers a temporary host error, it looks for a
retry rule for the host. If it can't find one, it looks for a retry rule
for the domain. Actually, it's a bit more complicated than that. It is
all explained in the manual. This is from section 31.1 of the 4.10
edition:

-----------------------------------------------------------------------
When looking for a retry rule after a routing attempt has failed (for example,
after a DNS timeout), each line in the retry configuration is tested only
against the domain in the address. However, when looking for a retry rule
after a remote delivery attempt has failed (for example, a connection
timeout), each line in the retry configuration is first tested against the
remote host name, and then against the domain name in the address. For
example, if the MX records for "a.b.c.example" are

  a.b.c.example  MX  5  x.y.z.example
                 MX  6  p.q.r.example
                 MX  7  m.n.o.example


and the retry rules are

  p.q.r.example    *      F,24h,30m;
  a.b.c.example    *      F,4d,45m;


then failures to deliver to host "p.q.r.example" use the first rule to
determine retry times, but for all the other hosts for the domain
"a.b.c.example", the second rule is used, and that rule is also used if
routing to "a.b.c.example" suffers a temporary failure.
-----------------------------------------------------------------------

--
Philip Hazel            University of Cambridge Computing Service,
ph10@???      Cambridge, England. Phone: +44 1223 334714.