A previously reported problem with Netscape Communicator is its slow typing speed when sending email. Tom Brown says that Netscape Tech Support offered a work-around: "Go to Preferences, then to Mail & Groups and then to Messages. Uncheck "By default, send HTML messages." It worked for Tom. However, he reports that you lose the ability to change a message's font, size, color, etc.
Update: Steve Dagley writes "The issue with slow typing in Communicator was one of the things addressed in the 4.01a release. The other major change in 4.01a, besides the security fixes, was a fix for slow to pull down menus on some machines."