Tagzilla
- An add-on to Mozilla that lets you add a tagline, random or specifically chosen by you, to the end of an email or newsgroup posting, or to the clipboard for pasting into a Web-based email or message board.
- http://tagzilla.mozdev.org/

Quote Colors
- An extension for the Mozilla Mail client that adds a user interface for configuring text and background colors for different quote levels when displaying messages.
- http://quotecolors.mozdev.org/

Mnenhy
- Enhancements to Mozilla Mail/News, Mozilla Thunderbird and Mozilla Firefox.
- http://mnenhy.mozdev.org/

MessageID-Finder
- An addon for the Mozilla mail/news client which helps you to find the message for a certain messageid.
- http://messageidfinder.mozdev.org/

EVM
- Allows you to store your email in a database in one or more categories, you can build categories by your own and rename them, and you can search email by attributes.
- http://evm.mozdev.org/

Enigmail
- An extension to the mail client of Mozilla / Netscape and Thunderbird which allows users to access the authentication and encryption features provided by the popular GnuPG software
- http://enigmail.mozdev.org/

Hermes
- A configureable way to read WebEmail Accounts automatically.
- http://hermes.mozdev.org/

Abzilla
- Adds Multiple AddressBook support to Mozilla. Contains experimental builds with the extension.
- http://abzilla.mozdev.org/