2.2.2 POP3 Server Messages

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This section defines the creation of POP3_AUTH_NTLM_Blob_Response messages. These are NTLM messages that are sent by the server and that must be encapsulated as follows to conform to syntax specified by the AUTH mechanism:

  1. Base64-encode the NTLM message data. This is needed because NTLM messages contain data outside the ASCII character range, whereas POP3 supports only ASCII characters.

  2. To the base64-encoded string, prefix the POP3 response code with a plus sign (+).

  3. Suffix the <CR> and <LF> character (ASCII values 0x0D and 0x0A) as required by POP3.

The ABNF definition of a server message is as follows.

 + <base64-encoded-NTLM-message><CR><LF>

De-encapsulation of these messages by the client follows the reverse logic:

  1. Remove the <CR> and <LF> character (ASCII values 0x0D and 0x0A).

  2. Remove the POP3 response code (+).

  3. Decode the base64-encoded POP3 data to produce the original NTLM message data.