Abstract: A secure e-mail service, executable on a recipient e-mail server or associated computer system, implements inverted security control over recipient content stored by the recipient e-mail server. Recipient content is received in conjunction with e-mail messages transmitted directed to recipients from sender computer systems unassociated with the secure e-mail service. The secure e-mail service includes a policy engine that operates on e-mail messages, as received from a communications network, to evaluate metadata features of the message and select a corresponding encryption key. The service further includes a content processing engine that operates to encrypt a portion of the message in a manner that allows subsequent decryption of said portion using the selected encryption key. A service interface enables transfer of the e-mail message, including the portion as encrypted, to the recipient e-mail server, which supports access by the recipients.