PHP Mobile Mail is aimed at mobile professionals who want to use their favorite MUAs (noteably pine or mutt) on their laptop, either in UNIX or Windows (under GNU Gygwin). This lets you work offline. It includes a mail_spooler program, which accepts the output of you MUA and spools (on, or offline). When connected, another process parses through the spool and sends your messages. It is also designed to "fake" using your REAL email address with free services like gmx.net, or mail.yahoo.com, when using their POP and SMTP servers, assuming you have a domain and account that you can control to this degree.
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.
FetchYahoo is a Perl script that downloads mail from a Yahoo! account to a local mail spool. It is meant to replace fetchmail for people using Yahoo! mail since Yahoo!'s POP service is no longer free. It downloads messages to a local mail spool, including all parts and attachments. It then deletes messages unless requested not to. It can also optionally forward messages to a specified email address and repeat with a given interval.
Tellmatic is a tool to manage and create newsletters for personalized mailing or mass mailing. Addresses and newsletters are stored in groups to handle different user groups and thousands of addresses at a time. SMTP is used for sending the newsletter to your subscribers to make sure you get all error and bounce messages. Bounces can be handled automagically via a small bounce-management module with POP3 access. It also has a small form-editor and statistics. You can import and export your addresses in CSV format.
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.
Vacation is a Horde module for managing user email "vacation notices" or "auto-responders." It works via a local vacation program and the .forward style forwarding mechanism supported by several popular mailers. Currently, it provides fairly complete support for managing .forward style vacation notices on Sendmail or Courier mail based systems via an FTP transport. It also has some support for LDAP, Qmail, and Exim SQL based servers.