Description:

tpop3d is yet-another-pop3-server. The intention has been to write a
server which is fast, extensible, and secure. `Extensible' is used
specifically in the context of new authentication mechanisms and
mailbox formats. Presently the distribution supports the following
authentication mechanisms:
- auth_pam - uses Pluggable Authentication Modules
- auth_passwd - /etc/passwd (and optionally /etc/shadow)
- auth_mysql - a vmail-sql style MySQL database; see
http://www.ex-parrot.com/~chris/vmail-sql/
- auth_pgsql - uses PostgreSQL database
- auth_other - an external program
- auth_perl - embedded perl subroutines

The latter four options provide virtual domain support; the first two
are designed to authenticate local (Unix) users.

The following mailbox formats are supported:
- bsd - for BSD (`Unix') mailspools
- maildir - Qmail-style maildirs
- empty - null driver

tpop3d implements an optional metadata caching scheme for BSD
mailspools, which offers improved performance in cases where many
users leave large numbers of messages on the server between sessions.