On Monday, August 26, 2013 15:42:41 Douglas Otis wrote: > Please also note that the PTR RR is not constrained in the current > specification and can create erratic results. It would be far safer to > Perm error when overflowing on the number of PTR records. There is no > upper limit as some represent web farms hosting thousands of domains. This exact issue was the subject of working group discussion. Since the number of PTR records is an attribute of the connect IP, it is under the control of the sending party, not the domain owner. A cap that resulted in an error would, as a result, enable the sender to arbitrarily get an SPF permerror in place of a fail if desired. The WG considered that not a good idea. Scott K