Back up mail server setup

Len Conrad lconrad at Go2France.com
Sat Sep 30 09:13:44 UTC 2000



>We have a qube to manage our web traffic.

what's that mean??

>We have set up the qube to act as a secondary mail server to kick in 
>when the G4 crashes.

backup MX, ok

>However, the qube does not deliver the mail, not while
>it is running nor once the main server is up again.

That could be an "issue".  "write-only" MX.  You'll need a big disk 
for the mail queue.

>As an individual client,  we can access the qube manually or rather 
>directly, but we
>don't seem to get routed through the DNS even though the qube is listed
>as secondary mail server in MacDNS with a larger value, ie.  10 mail.etc
>20 qube.etc We can't find any documentation for this scenario nor any
>settings that would have the qube check to see if the main mail server
>is back up again.

If the MTA on the qube is "smart" about MX (eg, as postfix can be), 
it will accept mail for domains for which the MTA discovers itself to 
be an MX and will automatically accept the domain's mail and try to 
relay such mail to the highest reachable MX, above itself, in preference value.

If the MTA is dumb about MX, then you have to tell the MTA which 
domains to relay  mail for AND the next-hop address to relay to, 
domain by domain.

>Is client access to/requests of DNS somehow different from incoming mail
>requests of DNS?

Mail clients talk mail protocols to mail servers.  DNS clients, aka 
resolvers, talk DNS protocols to DNS servers, essentially 
query/answer echanges.   SMTP mail servers talk to SMTP mail servers, 
not to DNS.

Mail delivery between you 2 mail servers has nothing to do with your 
DNS, after the resolver on the MTA sending learns the ip address of 
the destination MTA.

>Number 2:
>How can clients receive mail from the secondary mail server once the
>primary server has come back up?

They can't.  The mail clients read their mailboxes exclusively on the 
POP/IMAP server where their mailboxes are.  The secondary server is a 
relay-only server, it contains no mailboxes for the backed up MX 
domains.  The backup MX server must relay the backed up mail to the 
primary MX where the mailboxes are so the mail clients can read it.

>Number 3:
>Can primary mail server be set to retrieve mail collected on secondary
>server upon start up?

It's the secondary MX's responsibility to attempt to relay backed up 
mail to the primary MX, or any reachable MX of higher preference than itself.

>Number 4:
>Can qube se set up to pass all mail forward to primary server on a
>periodic basis thus delivering mail as soon as primary mail server
>starts up.

That depends on you qube mail server.  It must have some kind of 
"queue run timer" settting for retrying mail for unreachable servers.

You seem to have mail server problems, not DNS problems.

Len


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