NAME
popper - pop server

SYNOPSIS
/usr/etc/popper

DESCRIPTION
Popper is an implementation of the Post Office Protocol (version 3)
server that runs under MachTen to manage electronic mail for
Macintosh and MS-DOS computers. The server was developed at the
University of California at Berkeley and conforms fully to the
specifications in RFC 1081 and RFC 1082. The Berkeley server also
has extensions to send electronic mail on behalf of a client.

THE POP TRANSACTION CYCLE
The Berkeley POP server is a single program (called popper) that is
launched by inetd when it gets a service request on the POP TCP
port 110. The popper program initializes and verifies that the
peer IP address is registered in the local domain, logging a
warning message when a connection is made to a client whose IP
address does not have a canonical name. It also checks to see if a
cannonical name lookup for the client returns the same peer IP
address, logging a warning message if it does not. The the server
enters the authorization state, during which the client must
correctly identify itself by providing a valid Unix userid and
password on the server’s host machine. No other exchanges are
allowed during this state (other than a request to quit.) If
authentication fails, a warning message is logged and the session
ends. Once the user is identified, popper changes its user and
group ids to match that of the user and enters the transaction
state. The server makes a temporary copy of the user’s maildrop
(in /usr/spool/mail) which is used for all subsequent transactions.
These include the bulk of POP commands to retrieve mail, delete
mail, undelete mail, and so forth. When the client quits, the
server enters the final update state during which the network
connection is terminated and the user’s maildrop is updated with
the (possibly) modified temporary maildrop.

LOGGING
The POP server uses syslog to keep a record of its activities. The
server logs (by default) to the "local0" facility at priority
"notice" for all messages.

FILES
/usr/spool/mail mail files
/etc/inetd.conf pop program invocation
/etc/syslog.conf logging specifications