secondary MX (was Re: [TriLUG] co-lo or at home?)

[Lisa Lorenzin]

> Do you have/know of a quick and dirty "secondary MX" HOWTO somewhere?

there's probably one out there already, but here's how to do it.  i'd be 
happy to provide for you, if you're interested.

the person providing secondary MX (me) needs to set up their system to
allow relaying from the system of the person receiving (you).

on red hat 7.2 with sendmail, to do that:

edit /etc/mail/access and add the following line:

<domain.tld>                        RELAY

then run make in /etc/mail .

the person receiving secondary MX (you) needs to list the system of the
person providing as a second MX entry with a higher value (which
translates to a lower priority) than their primary MX.

to set your DNS up to use another person as a secondary:

[lorenzin at eeyore lorenzin]$ dig 1000plus.com MX

; <<>> DiG 9.1.3 <<>> 1000plus.com MX
;; global options:  printcmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 22408
;; flags: qr rd ra; QUERY: 1, ANSWER: 2, AUTHORITY: 2, ADDITIONAL: 2

;; QUESTION SECTION:
;1000plus.com.                  IN      MX

;; ANSWER SECTION:
1000plus.com.           346     IN      MX      0 mx.1000plus.com.
1000plus.com.           346     IN      MX      100 mx.elfie.org.

;; AUTHORITY SECTION:
1000plus.com.           83152   IN      NS      NS.elfie.org.
1000plus.com.           83152   IN      NS      NS.TECHNOMANCER.com.

;; ADDITIONAL SECTION:
NS.elfie.org.           97645   IN      A       207.198.61.53
NS.TECHNOMANCER.com.    167386  IN      A       216.254.85.146

and if your system drops offline, my system starts accepting and queuing
mail for you.  (i'm sure there's a default for how often it tries to
deliver it, and i'm sure it can be changed, but we didn't bother with 
that.)

it's just that easy (i love linux).  lemme know if you have any questions,
altho honestly that's about the extent of my clue here.

						lisa

-- 
lisa lorenzin  |  lorenzin at 1000plus.com  |  http://www.1000plus.com/lisa/
of what avail is an open eye if the heart is blind? - solomon ibn gavirol