On Sun, Jan 14, 2007 at 06:13:59PM -0600, Seth Goodman wrote:
Listing a large number of hosts by IP avoids additional queries to
resolve the names, but the resulting record can still be very long.
For many hosts, scattered around, the following could help:
"v=spf1 exists:%{ir}._spf.example.com -all"
This does need an additional lookup, but that's a small price to pay
when compared to "mx" or, worse, a lot of "include".
Beware when doing this: according to the DNS specifications no RR need
to be present at these domains, but in real life some DNS servers refuse
to answer "no error, zero answers".
Alex
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