I'm having a problem with bounceback e-mails sent to Yahoo addresses, and Lunarpages support is suggesting I establish an SPF record for my domain. I've looked at the SPF link they provided, I've looked at numerous topics on this forum, and I still don't have the foggiest idea as to what any of this means. I've copied the questions from the SPF Wizard and forwarded them to Lunarpages support, but they're telling me they can't help me answer these questions, and provided a link to this forum. Does anyone here know what to do with these? Thanks.

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lisamorton.com's IP address is 209.200.243.184 (pegasus.lunarpages.com).
Does that server send mail from lisamorton.com?

This wizard found 2 names for the MX servers for lisamorton.com: pegasus.lunarpages.com
and lisamorton.com. (A single machine may go by more than one hostname. All of them are
shown.)
MX servers receive mail for lisamorton.com.
Do they also send mail from lisamorton.com?

Do you want to just approve any host
whose name ends in lisamorton.com?

Do any other servers send mail from lisamorton.com?

You can describe them by giving "arguments" to the a:, mx:, ip4:, and ptr: mechanisms.
mx: takes domain names and approves all the MX servers of these domains. To keep the
wizard short we left out ptr:, but it works analogously.

IP networks can be entered using CIDR notation, eg. 192.0.2.0/24

Could mail from lisamorton.com originate through
servers belonging to some other domain?

If you send mail through your ISP's servers, and the ISP has published an SPF record,
name the ISP here.

Do the above lines describe all the hosts
that send mail from lisamorton.com?

In most cases, simply using a default SPF record would be sufficient.  This is:

yourdomain.com. IN TXT "v=spf1 a mx ~all"

This SPF record will authorize email coming from the server with the IP address of the server where you are hosted.  As long as you only send email SMTP on the server where you are hosted, this SPF record would work for you.  Normally, the only time when this SPF record would not apply is if you are hosting your email on a remote server (such as hosting your email with Google) or when you are using your Internet Service Provider's (ISP) SMTP server to send email.  You can check the SMTP/POP/IMAP servers in your email client's configuration.

Here are some links that may be helpful for learning more information on SPF records:
http://www.openspf.org/Introduction
http://www.openspf.org/SPF_Record_Syntax