Technical data

Configuring and Managing the POP Server
18.1 Key Concepts
18.1.4 How the POP Server Handles Foreign Message Formats
POP contains minimal support for mail messages that contain foreign formats.
Such messages are usually binary and therefore are not transferred to the POP
client. Instead, the POP server transfers the message headers, along with a brief
message instructing the user to log in and extract the foreign message into a file.
Foreign messages are moved into your MAIL folder; they are never deleted by the
POP server.
18.1.5 How the POP Server Authorizes Users
Table 18–1 outlines the methods the POP server process uses to authorize user
access.
Table 18–1 POP User Authorization Methods
Method Description
Shared secret-password
string
Most secure POP server access method. Initiated by the client system
through the APOP command.
Allows a user to become authorized by the POP server without the need
to send a password over the network. Eliminates a potential path for
unauthorized users to obtain a password and break into the system.
POP requires a shared secret string from any user who wants to read mail
using the APOP authorization method. For information about creating
the shared secret string, see the DIGITAL TCP/IP Services for OpenVMS
User’s Guide.
User name and password Least secure POP server access method. Initiated by the client system
through the USER and PASS commands.
The POP server authorizes the client to access the desired mailbox based
on receipt of a valid user name and password.
1. The user configures a user name and password into the POP client
system. Each POP client has its own method of configuring. Note that
the user name and password pair is the user name and password for
the TCP/IP Services system, not for the POP client system.
2. The POP client sends the user name and password pair to the server,
and the server confirms the pair against that in the OpenVMS
SYSUAF file. Note that the password is sent unencrypted over
the TCP connection, which might cause security problems for some
environments. Upon authorization, the POP server allows access to
the user’s OpenVMS mailbox.
OpenVMS SYSUAF settings
on user accounts
Access to the POP server is not permitted if:
• Either the DISMAIL or DISUSER flags are set for the account.
• The account has expired according to the SYSUAF expiration date.
• Access has been denied because of an incorrect user name and
password.
Ability to disable the USER
and PASS commands
Allows the system manager to use the APOP authorization method for
all POP clients, the more secure means of user authorization. When you
disable the USER and PASS commands (by defining the logical name
TCPIP$POP_DISUSERPASS), the POP server responds to the commands
with a failure message.
Configuring and Managing the POP Server 18–3