SPF vs TXT with includes

Timothy Holtzen tah at NebrWesleyan.edu
Tue Nov 16 22:23:35 UTC 2010

Does anyone know what happens if a domain with an older TXT spf record
is included in a newer SPF spf record?  For example:

foo.com     IN     TXT    "v=spf1 mx a:mail1.foo.com a:mail2.foo.com ?all"

bar.com     IN     SPF    "v=spf1 mx a:mail1.bar.com a:mail2.bar.com
include:foo.com ?all"

Ideally the desire is that the authorized mail hosts at foo.com are also
authorized to send mail on behalf of the bar.com domain.  My question is
will the SPF record for bar.com be valid if foo.com only has a TXT spf
record or would foo.com need to have a record of the SPF record type? 
I'm guessing that BIND doesn't do the recursion to resolve the include
statement itself and this may be dependent on the mail agent doing the

Timothy A. Holtzen
Campus Network Administrator
Nebraska Wesleyan University

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