=head1 NAME

public-inbox-pop3d - POP3 server for sharing public-inboxes

=head1 SYNOPSIS

  public-inbox-pop3d [OPTIONS]

=head1 DESCRIPTION

public-inbox-pop3d provides a POP3 daemon for public-inbox.
It uses options and environment variables common to all
read-only L<public-inbox-daemon(8)> implementations,
but requires additional read-write storage to keep track
of deleted messages on a per-user basis.

Like L<public-inbox-imapd(1)>, C<public-inbox-pop3d> will never
require write access to the directory where the public-inboxes
are stored.

It is designed for anonymous access, thus the password is
always C<anonymous> (all lower-case).

Usernames are of the format:

	C<$UUID@$NEWSGROUP_NAME>

Where C<$UUID> is the output of the L<uuidgen(1)> command.  Dash
(C<->) characters in UUIDs are ignored, and C<[A-F]> hex
characters are case-insensitive.  Users should keep their UUIDs
private to prevent others from deleting unretrieved messages.
Users may switch to a new UUID at any time to retrieve
previously-retrieved messages.

Historical slices of 50K messages are available
by suffixing the integer L<$SLICE>, where C<0> is the oldest.

	C<$UUID@$NEWSGROUP_NAME.$SLICE>

It may be run as a different user than the user running
L<public-inbox-watch(1)>, L<public-inbox-mda(1)>, or
L<public-inbox-fetch(1)>.

To save storage, L</publicinbox.pop3state> only stores
the highest-numbered deleted message

=head1 OPTIONS

See common options in L<public-inbox-daemon(8)/OPTIONS>.

=over

=item -l PROTOCOL://ADDRESS/?cert=/path/to/cert,key=/path/to/key

=item --listen PROTOCOL://ADDRESS/?cert=/path/to/cert,key=/path/to/key

In addition to the normal C<-l>/C<--listen> switch described in
L<public-inbox-daemon(8)>, the C<PROTOCOL> prefix (e.g. C<pop3://> or
C<pop3s://>) may be specified to force a given protocol.

For STARTTLS and POP3S support, the C<cert> and C<key> may be specified
on a per-listener basis after a C<?> character and separated by C<,>.
These directives are per-directive, and it's possible to use a different
cert for every listener.

=item --cert /path/to/cert

The default TLS certificate for optional STARTTLS and POP3S support
if the C<cert> option is not given with C<--listen>.

If using systemd-compatible socket activation and a TCP listener on port
995 is inherited, it is automatically POP3S when this option is given.
When a listener on port 110 is inherited and this option is given, it
automatically gets STARTTLS support.

=item --key /path/to/key

The default private TLS certificate key for optional STARTTLS and POP3S
support if the C<key> option is not given with C<--listen>.  The private
key may be concatenated into the path used by C<--cert>, in which case this
option is not needed.

=back

=head1 CONFIGURATION

Aside from C<publicinbox.pop3state>, C<public-inbox-pop3d> uses the
same configuration knobs as L<public-inbox-nntpd(1)>,
see L<public-inbox-nntpd(1)> and L<public-inbox-config(5)>.

=over 8

=item publicInbox.pop3state

A directory containing per-user/mailbox account information;
must be writable to the C<public-inbox-pop3d> process.

=item publicInbox.<name>.newsgroup

The newsgroup name maps to a POP3 folder name.

=back

=head1 CONTACT

Feedback welcome via plain-text mail to L<mailto:meta@public-inbox.org>

The mail archives are hosted at L<https://public-inbox.org/meta/>, and
L<nntp://news.public-inbox.org/inbox.comp.mail.public-inbox.meta>,
L<nntp://4uok3hntl7oi7b4uf4rtfwefqeexfzil2w6kgk2jn5z2f764irre7byd.onion/inbox.comp.mail.public-inbox.meta>

=head1 COPYRIGHT

Copyright all contributors L<mailto:meta@public-inbox.org>

License: AGPL-3.0+ L<https://www.gnu.org/licenses/agpl-3.0.txt>

=head1 SEE ALSO

L<git(1)>, L<git-config(1)>, L<public-inbox-daemon(8)>,
L<public-inbox-config(5)>, L<public-inbox-nntpd(1)>,
L<uuidgen(1)>
