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Suppose you have the domain, and you have set the following SPF:

v=spf1 ~all

Now, I have the IP address, and I am also the administrator of I can specify


and then I can send emails from my machine, pretending it's one of the machines.

Is this a significant risk? Should I avoid using ptr in the SPF?

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1 Answer 1

up vote 2 down vote accepted

According to wikipedia using PTR will also forward confirm the PTR (IE might resolve to but points to

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Thanks. See also for a more reliable source. – Antonis Christofides Nov 14 '12 at 12:19

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