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Front cover - IBM Redbooks

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266 Lotus Security Handbook<br />

Message encryption<br />

SMTP, with support for the SMTP extensions, can ensure that the initial<br />

client-to-server communication has been correctly authenticated. This does not,<br />

however, guarantee that during transit every single SMTP hop along the way will<br />

use that same authentication.<br />

Figure 6-25 Advanced SMTP configuration settings<br />

Furthermore, the message itself is not encrypted. This can be solved by using<br />

another SMTP extension that ensures the SMTP communications (client/server<br />

or server/server) are encrypted using public/private key pairs. However, this<br />

again does not guarantee that the message, during transit, will be encrypted for<br />

every single SMTP hop all the way to the recipient. Even if it were possible to<br />

guarantee that the e-mail message was correctly authenticated with trusted<br />

SMTP servers and fully encrypted during its hops along the way from sender to<br />

recipient, it still does not avoid the possibility that the message was spoofed from<br />

someone else.<br />

Thus, the only sure way to provide confidentiality, authentication and integrity of<br />

any e-mail message is to make sure that the MIME content of the message is<br />

cryptographically manipulated (using different methods for encryption). Until

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