[cobalt-users] How to make a Backup MX Server with sendmail

["Al-Juhani" <aljuhani@xxxxxxxxx>]

Hello List ..

I have noticed some posts recently about configuring a Backup MX server.
I have just assigned a backup mail server (IBM) for our main Server (RaQ4).
Both machines are running sendmail.

Here is the procedure:


on the Primary Server (RaQ4):
=====================

from the GUI / Control Panel / DNS choose the domain and then add a low
priorty MX record as:

RaQ4Domain.com pointing to mail.BackupMailServer.com

save the changes and the DNS settings.


on the BackUp Server (IBM):
=====================

1. Enable /etc/mail/relay-domains and /etc/mail/mailertable from the
sendmail.mc configuration file:

FEATURE(`mailertable')dnl
RELAY_DOMAIN_FILE(`/etc/mail/relay-domains')dnl

add the second line above if not existing or hashed out.

Rebuild the config file after enabling these features:

m4 /etc/mail/sendmail.mc > /etc/sendmail.cf

2. Create/touch a file named relay-domains under the /etc/mail and insert
the domain name that you will need the backup for (RaQ4 in this example),
as:

RaQ4Domain.com

exist and save the relay-domains file.

3. pico /etc/mail/mailertable and add the format below:

RaQ4Domain.com [TAB] smtp:[mail.RaQ4.com]

-or-

if you want to redirect the emails to a local user on the backup server
modify as below:

RaQ4Domain.com [TAB] local:username

then update the database:
makemap hash /etc/mail/mailertable.db < /etc/mail/mailertable

Now if your main mail server (RaQ4) fails emails will be delivered to the
Backup machine
where it is kept in the QUEUE /var/spool/mqueue/.

The backup mail server will try to deliver the mail at whatever interval you
specify with the
-q flag when running sendmail.

The default -q value is 1 hour but you can change it to whatever you want:

/usr/sbin/sendmail -bd -q15m (for 15 minutes).

Other settings you can change in the sendmail.mc file are:

define(`confTO_QUEUEWARN', `4h')dnl
define(`confTO_QUEUERETURN', `5d')dnl

first line define the time (4 hours) after which the sender will receive a
warning message if the primary server (RaQ4) is still offline.

second line simply says if the primary mail server still not answering,
delete the queue and return the message as undeliverable to the sender.

Thats all ..

Just thought to share this info ...

Regards,

Al-Juhani
aljuhani@xxxxxxxxx