Mailpictures is a Nautilus extension in GTK/Perl, designed to be a more featured nautilus-sendto replacement. It allows direct access via Nautilus context menus, automatic resizing of pictures, setting for JPEG compression, ZIP archiving of the selection, support for Evolution, Thunderbird, Icedove, and Kmail, and the ability to save results in a folder.
Bulk Mac Mail is an an application for sending personalized mass email messages. It allows you to use message templates with multiple custom fields from the recipient database inside your messages. Customer lists can be imported from files of any type. Since all messages go through the standard Apple Mail's message delivery framework, they are absolutely indistinguishable from the messages that were actually sent by Apple Mail.
Trojita is a Qt IMAP email client. It is a pure Qt4 application with no additional dependencies. It has a robust IMAP core implemented using Qt's Model-View framework. Standards compliance is a design goal. It has support for bandwidth-saving mode aimed at mobile users with expensive connections. In addition to the usual SSL/TLS connections, the server can be accessed via SSH. It has on-demand body part loading, offline IMAP support, and safe dealing with HTML mail (actually more robust than Thunderbird's).
smtp-cli is an SMTP command line client with support for advanced features such as STARTTLS, SMTP-AUTH, or IPv6. It also has scriptable message composition capabilities supporting anything from simple plain-text messages right up to building complex HTML emails with alternative plain-text part, attachments, and inline images. It's also a convenient tool for testing and debugging SMTP servers' setups. smtp-cli can be used to check a given server's capabilities, to test your server's setup, or to create and dispatch email messages. The command line interface is intuitive, and everything is scriptable and can run in a completely non-interactive mode from scripts or cron jobs. smtp-cli is ideal for shipping log files from remote machines, running periodic mail delivery test loops, etc.
Yasma (Yet Another Sendmail Logfile Analyzer) is a reporting tool for sendmail log files. It provides a nice overview of your mail traffic like: messages transferred, some average values, top lists of messages sent, received, rejected, etc., and top lists of supposed spammers, status messages, relay hosts, and mailers. It analyzes one or more log files from the command line and writes an HTML report. For security, it can hide the user part of mail addresses listed in the report. A GeoIP database can be used to show country information.