How to install dkim for postfix in centos 5.4

Question

I am trying to install DKIM for my postfix so that i have a signature. I am following this guide: http://allaboutlamp.com/2009/09/setup-dkim-for-postfix-in-fedora-using-dkim-milter/

But how do i create a DNS record for TXT ? Where is the file. My originaldomain.com is running in a hosted server, where i dont have terminal access. And i have another server where i am trying to install this setup. Which is only for outgoing emails for newsletters.

Step 1:
[root@out tmp]# openssl genrsa -out rsa.private 1024
[root@out tmp]# openssl rsa -in rsa.private -out rsa.public -pubout -outform PEM
[root@out tmp]# ls
rsa.private  rsa.public

Step 2: How can i know assign dkim postfix signatures?
[root@out tmp]# yum list dkim-milter
Loaded plugins: fastestmirror, replace
Loading mirror speeds from cached hostfile
 * addons: ftp.heanet.ie
 * base: ftp.heanet.ie
 * epel: ftp.heanet.ie
 * extras: ftp.heanet.ie
 * ius: mirror.rackspace.com
 * rpmforge: apt.sw.be
 * updates: ftp.heanet.ie
Installed Packages
dkim-milter.x86_64                                                                                     2.8.3-4.el5                                                                                      installed
[root@out tmp]# 

Answer 1

I have had good success using DKIMProxy. Check out this article: http://www.brandonchecketts.com/archives/getting-dkimproxy-installed-and-configured

And in your comments to @mattdm you are confusing SPF with DKIM-Signature. Both use DNS TXT records but they are separate things/records. With some Registrars/DNS Providers you need to turn on "Advanced DNS Records" or similar description in order to create TXT records.

You basically publish the public part of your key in the TXT record for DKIM-Signature.

HTH

Cheers

Answer 2

But how do i create a DNS record for TXT ? Where is the file.

There's not a file. A TXT record is a certain type of response to a DNS query, just like an A record provides an IP address for a name, or a CNAME record provides an alias. You can't change it on your mail server — you need to update the records associated with your domain name.

My originaldomain.com is running in a hosted server, where i dont have terminal access.

You don't need terminal access. You need to talk to the company that hosts your DNS service. This is probably the site that you registered "originaldomain.com" with. (Note, though, that that's actually a real domain that belongs to someone. Use example.com for examples.) It may be your a web hosting provider or someone else, though. (It's rare for small or even moderate-sized organizations to run their own DNS servers these days.)

So, you need to look in the web interface those people provide you, and if there's no obvious way to set a TXT record, you should contact their tech support. And if they can't help you, you should strongly consider moving your domain name to a better service.