getmail is intended as a simple, secure, and reliable replacement for fetchmail. It retrieves email (either all messages, or only unread messages) from one or more POP3, SPDS, or IMAP4 servers (with or without SSL) for one or more email accounts, and reliably delivers into qmail-style Maildirs, mboxrd files, or through external MDAs (command deliveries) specified on a per-account basis. getmail also has excellent support for domain (multidrop) mailboxes, including delivering messages to different users or destinations based on the envelope recipient address.
vpopmail (vchkpw) is a collection of programs and a library to automate the creation and maintenance of virtual domain email configurations for qmail installations using either a single UID/GID or any valid UID/GID in /etc/passwd with a home directory. Features are provided in the library for other applications which need to maintain virtual domain email accounts. It supports named or IP-based domains. It works with vqadmin, qmailadmin, vqregister, sqwebmail, and courier-imap. It supports MySQL, Sybase, Oracle, LDAP, and file-based (DJB constant database) authentication. It supports SMTP authentication combined with the qmail-smtp-auth patch. It supports user quotas and roaming users (SMTP relay after POP authentication).
qpsmtpd is a flexible smtpd daemon written in Perl. Apart from the core SMTP features, all functionality is implemented in small "extension plugins" using the easy-to-use object oriented plugin API. qpsmtpd was originally written as a drop-in qmail-smtpd replacement, but now it also includes an smtp forward and a postfix "backend".
SPF is a new strategy for preventing junk mail. The present SMTP standard for email allows anyone to forge anyone else's email address. SPF verifies that the Sender address of an email message matches (according to some policy) the client IP address that submitted it. libspf2 is a complete and robust implementation of SPF which provides support for many MTAs. Support for new MTAs is in progress.
SubEthaSMTP is an easy to understand Java library that provides a receptive SMTP server component. By plugging this component into your Java application, you can easily receive SMTP mail using a simple abstract Java interface. Also included is a small sub-project called Wiser, an easy to use incoming mail testing framework.
Net_NNTP is a PHP/PEAR library for communication with NNTP servers. Net_NNTP handles connection and protocol-level commands (RFC977), including many non-standard commands (RFC2980), via a user-friendly API which hides the actual NNTP commands/syntax. Some knowledge about NNTP and general knowledge about email and MIME is required, since parsing of content and headers is left up to the user. Net_NNTP allows advanced users direct usage of NNTP commands via the separate protocol implementation. Net_NNTP includes a fully-functional NNTP to HTML gateway demo application.