P

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Parent domain

A Windows domain that has another domain subordinate to it in the DNS namespace.

PFH

Public Folder Hierarchy. Exchange 2000 and 2003 support multiple public folder hierarchies, whereas previous versions only supported the single default hierarchy.

PKI

Public Key Infrastructure. A system of digital certificates, certification authorities, and other registration authorities that verify and authenticate the validity of parties engaged in an electronic transaction.

POP3

Post Office Protocol Version 3. An Internet client messaging protocol that Exchange supports.

Private key

One half of a key pair that is kept private to a user and then used to decrypt data encrypted with a user's public key.

PTR

A DNS pointer record that maps an IP address to an FQDN. Often referred to as a reverse lookup record.

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