Question about MX records
Barry Margolin
barmar at alum.mit.edu
Mon Mar 8 21:21:29 UTC 2004
In article <c2idv8$otu$1 at sf1.isc.org>, vo at eudoramail.com (John) wrote:
> Hi all:
>
> I have two mail servers:
>
> IN MX 10 server1 preferred.
> IN MX 20 server2 second choice.
>
> My questions are:
>
> 1. What is considered failure? if server1 has a problem
> and gives the incoming connection "connection refused"
> message? will the sending mail server jump to server2
> then? how does the dynamic work?
Yes, a failed connection attempt -- either a timeout while trying to
connect or a connection refused -- is the only thing that will cause
most mailservers to fail over to a backup MX. I think RFC 2821
recommends also failing over due to certain types of errors encountered
after connecting successfully, but I don't know if many mailers have
been updated to conform to this.
> 2. If the DNS server that the incoming mailserver uses
> had cached the info including the old server1 info,
> will the mail server then keep trying it even though
> it's down?
It will keep trying them in order -- first server1, then server2.
BTW, do you have a question about the BIND nameserver? It seems like
your questions are about mailservers, and would be more appropriate in a
mail-related newsgroup.
--
Barry Margolin, barmar at alum.mit.edu
Arlington, MA
*** PLEASE post questions in newsgroups, not directly to me ***
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