SPF records question

[subt1e]

I would like to get some clarification on some instructions I am following that involve changing my spf records. (This is involving Google Apps and Message Security and Discovery Activation Guide for postini)

I am asked to do the following:

1. Enter the following in my SPF record

yourdomain.com. IN TXT "v=spf1 include:spf.yourdomain.com -all"

Where do I need to go to make modifications to SPF records. And it seems that I need to create a spf subdomain?

2. Add the following TXT Record to spf.yourdomain.com:

spf.yourdomain.com. IN TXT "v=spf1 ip4:207.126.144.0/20 ip4:64.18.0.0/20 ip4:<yourdomain.com IP allocations> -all"

This seems like just making similar modifications to spf records, but this time to the subdomain. correct?

Thank you.

[subt1e]

What is the purpose of creating a subdomain?

Can't I just add the following to my domain.com.
IN TXT "v=spf1 ip4:207.126.144.0/20 ip4:64.18.0.0/20 ip4:<yourdomain.com IP allocations> -all"

[r2b2]

You can indeed just put the SPF record as stated directly on your domain. I'm guessing the reason they suggest doing the subdomain thing is so that you can reuse the SPF record on multiple domains (i.e. have three domains pointing to spf.yourdomain.com so that when you alter one SPF record you alter it for all three)

However if you've only got one domain, then just stick it on the domain...

[subt1e]

Thank you r2b2.

One more question.

For <yourdomain.com IP allocations>, can I put my hostmonster shared IP, or will I have to pay for a static IP?

[r2b2]

Instead of putting ip4:<yourdomain etc.>, stick in "include:hostmonster.com"

This way you'll automatically pick up the SPF record for hostmonster.com which includes the variety of mail servers that they have (the mail doesn't actually come from the hostmonster shared ip address, it comes from one of their multitude of mail servers)