Books

Better, Faster Email : Getting the Most Out of Email
A good overall reference for general e-mail usage. Good information on how to use e-mail as the tool it was meant to be.
Outlook 98 for Dummies
There is no question that Outlook 98 is a large application loaded with features. This book will walk you carefully through the majority of Outlook 98 features.
Mastering Microsoft Outlook 98
This book deals a lot with using Outlook 98 as a PIM (Personal Information Manager). If you want to get the most out of Outlook 98, this book will help.

Web Resources

Eudora
Probably the most popular e-mail client software around. Eudora is also one of the best.
Click here to jump straight to the free version, Eudora Lite.
Microsoft Outlook
A very popular e-mail client and Personal Information Manager (PIM).
Netscape Communicator
Although Netscape Communicator is a full suite of products, the e-mail client, Netscape Messenger, is very popular and easy to use.