Althea is an IMAP email client for X that uses the GTK widget set. It was built with the IMAP protocol in mind in order to avoid many of the pitfalls experienced by POP clients that added IMAP support. Althea allows easy access to a nearly unlimited number of servers, and has a very small memory footprint. As of version 0.5.0 Althea also supports IMAP over SSL.
The AMC Mail Client is a mail client striving to be a robust, fully gnome-compliant mail reader. However, the AMC Mail Client differs from other mail clients in that it attempts to utilize existing tools for mail retrieval, sending, and filtering, (fetchmail, sendmail/smtp, procmail). By not going through the process of reinventing the wheel, the AMC Mail Client starts out as a fully equipped client that inherits all of the features of these existing tools.
This is a PHP class that attempts to validate a given e-mail address at three levels: matching the address against a RFC compliant regular expression, verifing the existence of the destination SMTP server by verifying the respective DNS MX record, and connecting to that server to see if the given address is accepted as a valid recipient. The class also features a debugging output option that lets you see the remote SMTP server connection and data exchange dialog to see the real cause why an apparently valid address may not be accepting messages.
MailMan is one of the most stable, mature, and robust Web-based email systems available. The overall goal of the system is to provide the simplest possible way to add a Web-based email system to any Web site, so ease of installation and maintenance was the first goal in MailMan's design. It has no dependencies and no known incompatibilities with any Web server or mail server. It supports sending and receiving attachments, a single-frame or multi-frame interface, HTML-formatted messages, user options, address books, mail folders, and more.
Evolution is the GNOME mailer, calendar, contact manager, and communications tool. Evolution represents the next step forward in GNOME applications. The tools which make up Evolution will be tightly integrated with one another and act as a seamless personal information-management tool.
GMailWatch is a GNOME Panel Applet that displays a summary of incoming mail (sender/subject) rather than just an icon. It's similar to the old xmailwatcher utility (and uses some of the same code), and is also based upon mailcheck (of gnome-core). The user can change the size of the panel applet.