Composing e-mail

When I try to compose an email message I get a box telling me to okay an addin (Java  RTE) .  When I okay it, I get another message telling me "certificate" has been revoked and I am "locked out" of composing email messages.  I have reinstalled Java Runtime Environment and there's no difference.  Another email program I am using (since Cox Webmail doesn't work) is Thunderbird and there's no problem composing and sending email  messages.  I prefer using the same email program for both receiving and sending messages.  Don't like having to go to another program in order to send a message.  I must be doing something wrong.  I talked on line with a Cox person and she had no clue about what I was talking about.  Can anybody help me?