In last month's article we set up dns as a name server for network. Sendmail, and most other mail transport programs, use dns to decide where to send the mail, but we need to modify it a bit. The name-to-ip file has to have a MX line for each computer, which essentially says: for this computer, use this other computer for storing mail.
The file from last month looks like this. Note, the *** are not part
of the file:
**************************************************************
@ IN SOA master.kulai.org. jpollman.kulai.org. (
1;
10800;
3600;
604800;
86400 );
IN NS master.kulai.org.
master IN A 192.168.124.10
mail IN A 192.168.124.10
www IN A 192.168.124.10
news IN A 192.168.124.10
localhost IN A 127.0.0.1
fserver IN A 192.168.124.11
jc IN A 192.168.124.1
phillip IN A 192.168.124.20
**************************************************************
We change this to add in the MX lines. Note: the Bold items are explained below and are not part of the format of the file. It now looks like this:
**************************************************************
@ IN SOA master.kulai.org. jpollman.kulai.org. (
2
10800
3600
604800
86400 )
IN NS master
IN MX 10 master
master IN A 192.168.124.10
master IN MX 10 master
mail IN A 192.168.124.10
www IN A 192.168.124.10
news IN A 192.168.124.10
localhost IN A 127.0.0.1
fserver IN A 192.168.124.11
fserver IN MX 10 master
jc IN A
192.168.124.1
jc IN
MX 10 master
phillip IN A 192.168.124.20
phillip IN MX 10 master
**************************************************************
Now each computer's (master, fserver, jc, phillip) email server is
master.kulai.org (actually it is called a "mail exchanger", but since we
have only one computer server mail, it functions as a email server.) We
also have a line with no name that points to master.kulai.org as the email
server - this is for the domain: kulai.org. You noticed there is a "10"
in each line. The number, 10 in this case, is a relative value, and
is used when you have multiple mail exchangers - something we are not covering
here. Note, failure to put the number in will cause an error in named.
Now, restart named, and check /var/log/messages for any errors.
You have to put a line in for each computer: kulai.org by itself will
not work.