On Thu, March 26, 2009 19:19, Kevin Darcy wrote: >> 2) What is the maximum number of includes inside a SFP field? >> > I assume you mean SPF (Sender Policy Framework), the anti-SPAM(ming) > mechanism (?) > > I'm no SPF expert but in glancing at the documentation it looks like > there is no arbitrary limit on the number of "include"s. Since SPF > "records" are stuffed into (one or more?) TXT records, the above limits > in the answer to question #1 would apply.
Kevin, it looks like you are correct. From the RFC: -------- 3.1.4. Record Size The published SPF record for a given domain name SHOULD remain small enough that the results of a query for it will fit within 512 octets. This will keep even older DNS implementations from falling over to TCP. Since the answer size is dependent on many things outside the scope of this document, it is only possible to give this guideline: If the combined length of the DNS name and the text of all the records of a given type (TXT or SPF) is under 450 characters, then DNS answers should fit in UDP packets. Note that when computing the sizes for queries of the TXT format, one must take into account any other TXT records published at the domain name. Records that are too long to fit in a single UDP packet MAY be silently ignored by SPF clients. -------- So, it appears that you can as many include's in a SPF record as you wish, but it would be wise to keep the size of the SPF record below ~450 characters. There is lots of good SPF information at www.openspf.org -Vince _______________________________________________ bind-users mailing list bind-users@lists.isc.org https://lists.isc.org/mailman/listinfo/bind-users
