[oclug] Question about MX records

[Howard Krakower]

I know this is a bit off-topic, but still may be of interest. . .

In creating the zone file for DNS records, there is an option to add
an MX record - i.e., to point to a mail exchange. Normally, if you
have a single domain, such as foo.com, the MX record in the zone file
would say

MX 5 foo.com

this would indicate that an MX with a priority of 5 sends mail to
mail.foo.com

to provide for uninterrupted mail in the event that mail.foo.com is
down, a secondary MX might be there pointing to, say, mail.second.com
in the manner

MX 5  foo.com
MX 10 second.com

Then, if mail was undeliverable to foo.com because the connection was
down, it would be delivered and queued up on second.com. As soon as
foo.com is connected, second.com would forward all the mail it held
for foo.com.

Now, for the question:

What records, if any, are necessary for second.com to have in its zone
file? While sendmail.cf would have to indicate that it acts as a
secondary MX, what, if any, changes would have to be to second.com if
it uses qmail?

Howard Krakower

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