EMAIL encryption when using Firefox

I am trying to find a program that will encrypt my email (hence this forum vs. software). I need something SIMPLE - I would like to open Firefox, type in my message, click on ENCRYPT then have the program encrypt it so the receiving person can enter a key (which I have already provided) and then the msg would automatically decrypt. I have downloaded a few and they either needed keys/certificates (which I never received/downloaded); would not find the window in 'focus' so got "no text seen" msgs; needed true mail programs like Outlook or Thunderbird; could NOT make a self decrypting msg (once provided key was entered by the recipient <as they may not have the encryption program installed on THEIR computer>) and on....I really don't want to create the text in a Word window - encrypt it and then cut and paste into the Firefox msg window. Does anyone know of or IF such a program does exist?? Thought I had it in a program called Flexcrypt but cannot get it to encrypt as it is supposed to. ANY help or name of a program would be appreciated. THANKS...

Thanks for responding.... Can I assume that you use this program or perhaps did? I must be doing something wrong. I must be doing something wrong and perhaps you can tell me what that is. I opened Mozilla Firefox, and then copied the link to my bookmark page as it states. I then go to Yahoo mail and then click on the NEW MAIL button and enter the name to receive the email, title, etc. I then type the body. When finished I click on the Encipher It 'button' and it says "message cannot be found". HOW can the msg not be found when I am in the mail create page and the text is right there???? ANY help appreciated. It seemed so simple! Thanks..

This may be what you are looking for: How To Encrypt Email Messages in Firefox