SPF record for Exchange 2010

I want to install/create an SPF record for my domain -- let's see it mydomain.com. I also have another domain on that mail server, let's call it mydomain2.com.  
I'm noticing that some mail from outside hosts(outlook.com)  are going directly into my users junkmail folder, and the message in the headers of these say:
received-spf: None (protection.outlook.com: mydomain.com does not designate permitted sender hosts

I found a wizard out there that creates SPF records but I'm not 100% clear on all of the questions it's asking.
In particular these three:
1. Enter any IP addresses in CIDR format for netblocks that originate or relay mail for this domain
(space separated, for a single IP address use /32, i.e.
2.Enter any other hosts which can send or relay mail for this domain
(space separated)
3. Enter hostnames for any remote spf records to include
(ex. include:_spf.google.com, space separated)

Can someone help me with these questions or point me to a good generic SPF example file.

Last, if I mess up the SPF file and don't put in all the correct data, what's the worst that can happen?  Can it cripple my mail server?
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The SPF records define what mail server by ip address is allowed to send mail for a given domain.

Typically you would put the WAN ip address of your mail server (or firewall if the default gateway) in the record for each domain.

For example, your spf record might look like the following.

v=spf1 ip4: ip4: -all

This says that these two ip addresses are allowed to send mail for the given domain. Since the spf record goes on your ISP's resolution for your domain, there is no domain name in the actual record.

There is a lot of additional information here if you need it:

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