1.0 link Rainbow Dash Network http://rainbowdash.net/ Bit Shift (bitshift) http://rainbowdash.net/bitshift http://rainbowdash.net/notice/1881655 @<span class="vcard"><a href="http://rainbowdash.net/user/2959" class="url" title="Kaiba (formerly Ponydude)"><span class="fn nickname">widget</span></a></span> SPF is Sender Policy Framework. It's a TEXT (usually - there's one other valid type, but I don't recall it) record in DNS that basically says &quot;these IPs are the only ones meant to be sending mail that claims to be from this domain&quot; - if the sending machine's IP isn't on there, most of the big mail providers will just silently drop mail from it.