http://spf.pobox.com You can use this link and generate SPF record text line including IP ranges to include as a safe list. SPF records are still complex to implement and can easily get your IPs listed in the black list. If you use ISP mail servers to send out email appearing from your domain you will have to list your isp domain, and you personal ISP assigned IP range as a safe side.
In case any of your IPs are banned to send any further emails you will have to login a free account at Sorbs.net and get your IP Delisted. Also note that SPF records are propagated just like DNS records and any further change in SPF records might take upto 48hrs to kick in.
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