ipopd.8c

SIP（Session Initiation Protocol）是由IETF定义

.TH IPOPD 8C "January 16, 1992"
.UC 5
.SH NAME
IPOPd \- Post Office Protocol server
.SH SYNOPSIS
.B /usr/etc/ipop2d
.PP
.B /usr/etc/ipop3d
.SH DESCRIPTION
.I IPOP2d
and
.I IPOP3d
are servers which support the
.B POP2
and
.B POP3
remote mail access protocols respectively.
.I IPOP2d
and
.I IPOP3d
can also be used by
.B POP2
and
.B POP3
clients to access mailboxes on
.B IMAP
servers by specifying a login user name in the form <host>:<user>
e.g.,
.B SERVER.WASHINGTON.EDU:SMITH.
.PP
.I POPd
is invoked by the internet server (see
.IR inetd (8)),
normally for requests to connect to the
.B POP
port as indicated by the
.I /etc/services
file (see
.IR services (5)).
.SH "SEE ALSO"
imapd(8C)
.SH BUGS
The
.B POP2
and
.B POP3
protocols are intrinsically less flexible than
.B IMAP
and do not maintain `read' vs `unread' state on the server.  As a result,
most
.B POP
based software transfers all the mail from the server to the client and
deletes it from the server.  This necessarily locks the user into using only
a single client.
.PP
.B POP3
does not allow you to specify an alternate folder from the user's default.