HP-UX System Administrator's Guide: Configuration Management

mail. On HP-UX and other UNIX systems, the primary Mail Delivery Agent is
sendmail.
Although sendmailcan be run directly from a shell command line to send a message,
it is not usually used in this way. Mail User Agents are usually used as front ends to
sendmail for sending mail.
Mail Delivery Agents:
• Deliver mail to local users (users receiving e-mail on the computer that the Mail
Delivery Agent is running on) by scheduling the /usr/bin/mail program or by
forwarding the mail to users on local client machines.
• Forward e-mail via the appropriate transport mechanism not intended for local
users to other computers/networks for delivery. For example, UUCP mail would
be sent on its way by scheduling (and passing the message to) the uux program.
• Modify the format of the address information in message headers to accommodate
the needs of the next computer or network in a message’s delivery path, and to
accommodate the delivery method that is being used to route the message. For
example:
UUCP addresses are of the form:
[e-mail]!username
whereas TCP/IP addresses can take one of several forms, such as:
user
user@computer
[e-mail]
Mail Alias Files
Mail Alias Files are used for:
• Mapping “real world” names to user login names
• Describing distribution lists (mailing lists), where a single name (for example,
deptXYZ) is mapped to several or many user login names
For faster access, the alias files can be processed into a hashed database with the
command newalias (a form of sendmail). By default, the system alias file (ASCII
version) is located in the file /etc/mail/aliases.
The Mail Queue
Outgoing messages cannot always be sent right away because of down computers,
broken network connections, network traffic, and other reasons. Your Mail Delivery
Agent needs a place to hold these messages until they can be sent on their way. That
place is the mail queue.
If you are using sendmail (supplied with HP-UX) as your Mail Delivery Agent, your
mail queue is, by default, the directory /var/spool/mqueue.
122 Configuring Mail