[CentOS] question regarding mx servers with same priority

nate centos at linuxpowered.net
Tue Jul 15 21:58:31 UTC 2008

fabian dacunha wrote:

> a) do i have to create all the existing user accounts on my existing email
> server to this new server
> cause i already hav about 300+ email users already

Depends what you want to accomplish, for the simplest of setups,
no. You can (depending on the MTA of course), simply route all mail
for a particular domain or host name to another system.

In postfix this is accomplished like this:
(snip the usual basic config)
transport_maps = hash:/etc/postfix/transport
local_recipient_maps = proxy:unix:passwd.byname, $alias_maps,

then in /etc/postfix/local_recipient:

and in /etc/postfix/transport:
mydomain.com         smtp:name_of_other_smtp_server

run postmap hash:/etc/postfix/local_recipient
run postmap hash:/etc/postfix/transport
restart postfix and off you go.

If you want to reject mails for invalid users at the backup MX then
you can probably put the user names in the local_recipient file above,
create the accounts on the system, or use a distributed authentication
database like SQL, LDAP etc. My preference is the above blind forward
method, if the user is invalid then the server will reject it, I don't
care if it sits in the queue for a few days on the backup system.

> b) incase my first email server fails are the emails on the first server
> lost

Depends on what you mean by fail and depends if the mail on the first
server is stored there or if that system simply forwards on to another
host for delivery to users. If the users that read mail access it from
that system, and that system bursts into flames, and the mails happen
to sit on internal storage inside the system(as opposed to a NAS or
a SAN) then yes mail stored on that system is lost. If the system
simply crashes and needs to be rebooted then it is likely nothing
is lost.


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