Newbie needs help

Hi

Having been receiving over 2000 unwanted emails today I finally have to do
something about it and my domain supplier told me about spf.

I have two mailboxes linked to two separate domains (one POP and one IMAP)
and I connect through my cable account. I also use the mailbox supplied by
the cable supplier. I seem to be experiencing the problem with only one
domain at present, although ideally I would like to protect them all.

I have looked at the wizard, but am a little confused when it comes to
transferring any settings to the DNS server.

I'm currently running Windows XP SP2 and (if it make any difference )
Outlook 2007.

My computer knowledge is OK, but not entirely clear when it comes to DNS
settings etc...

I hope that someone can assist please.

Kind Regards

Stephen