Sylpheed is a
GPLed
GTK+-based
email/
Usenet client for
POSIX compliant OSes like
Linux. The main author is
Hiroyuki Yamamoto. According to the FAQ, the name Sylpheed means "light weight", like air, and is inspired by the
Sylphs, wind spirits.
Sylpheed was designed to be fast, easy to use, highly configurable and full of features. The interface is the standard three panes for folders, messages and message text, although everything is selectable through keyboard shortcuts. Messages are stored in the relatively uncommon MH format, where each folder is a directory and each message is a file, and mbox files can be imported or exported. Sylpheed natively supports the POP3, APOP, IMAP, SMTP, SMTP AUTH, and NNTP protocols, and also uses the local mail spool or user-configured external programs such as fetchmail. Sylpheed displays the text of HTML mail, but doesn't format it or display images from web servers, avoiding spam web bug confirmation. Sylpheed also does multiple mail/news accounts, thread displays, filtering, MIME attachments, internal image views, user-defined headers, colored labels, passthrough to external editors, message queueing, templates, line-wrapping, IPv6, i18n through gettext, and code set support for various non-English languages. Sylpheed also supports numerous other features with the appropiate libraries, such as X-Face, GnuPG-signed and encrypted messages with the GPGME library, and SSL for message recieving/sending with OpenSSL.
While various feature-enhancing patchs for Sylpheed exist, the majority of bleeding edge development takes place in the sylpheed-claws branch. It offers better GnuPG support (such as passphrase storing), LDAP support through OpenLDAP, better line-wrapping, spell-checking with pspell and aspell/ispell, theme support, better filtering, scoring, address harvesting, and selective downloads of mail (very handy for removing large unwanted emails).
A more experimental branch is the Windows port using Gtk+ Win32, available in both regular and claw branches. It requires a bit of Registry work and numerous support libraries to run.
Personally, I use sylpheed-claws. Although it's under heavy development I haven't had a problem with stability or message corruption. It starts up in about a second, filters all my various mailing list and frequent correspondents' messages into the appropiate folders, corrects my spelling, supports GnuPG, and tells HTML mail to go bite itself. Mailwise, it does everything I want - well, except for Ximian Evolution's nifty Virtual Folders option, but then again it's twenty times faster and a lot lighter. For Usenet, I prefer Pan, however - sylpheed works for news, but it's not as specialized.
Sylpheed is available from http://sylpheed.good-day.net
Sylpheed-claws is available from http://sylpheed-claws.sf.net
Sylpheed/Win32 is available from http://claws-w32.sourceforge.net/