In Netscape Communicator 4.7 (on Macs, but I believe the method is the same on non-Macs)
Go to Edit/Preferences
Then under Catagory
Mail & Newsgroups/Messages
at the bottom of the window where it says "Send messages that use 8-bit
characters"
check
As is (does not work well with some mail servers)
then click
OK
button
If one's messages then don't work, one can
A. complain to their server
B. change servers
C. keep sending MIME messages that irritate the recipients
D. sell the computer for scrap and go back to writing letters