The SeaMonkey project is a community effort to develop an all-in-one Internet application suite. It contains an Internet browser, email and newsgroup client with an included Web feed reader, HTML editor, IRC chat, and Web development tools, and is sure to appeal to advanced users, Web developers, and corporate users. It uses much of the Mozilla source code powering such successful siblings as Firefox, Thunderbird, Camino, Sunbird, and Miro.
LibESMTP is a library to manage posting (or submission of) electronic mail using SMTP to a preconfigured Mail Transport Agent (MTA) such as Exim. It may be used as part of a Mail User Agent (MUA) or another program that must be able to post electronic mail but where mail functionality is not the program's primary purpose. LibESMTP is not intended to be used as part of a program that implements a Mail Transport Agent.
PHPMailer is an email transport class which features multiple file attachments, CCs, BCCs, REPLY-TOs, HTML messages, redundant SMTP servers, and word wrap, among others. It can send email via sendmail, PHP mail(), or with SMTP. Methods are based on the popular AspEmail active server component.
ora_mail is a tool for those of us who do not want to enable JServer for one reason or another. It is implemented as an external procedure that reads message data from CLOBS and passes it to and external program, such as qmail-inject or sendmail. There is also PL/SQL package that wraps arround this procedure to ease message creation.
libspopc is an easy-to-use POP3 client library written in C. It implements the client side of RFC 1939, providing an easy and quick way to support POP3 and POP3s (SSL) access in a program. It can download email headers and delete messages remotely without actualy downloading the message.