Unfortuntely... email is inherently insecure. The only way I know of to send truly secure emails is to use an encryption program to encrypt or "code" the message before sending.
Then the person recieving the message must have the same encryption program and a "key" to unlock the message when they receive it. Not very practical for everday use ... otherwise anyone/anywhere between you and the recipient with a 'packet sniffer' can read all they want.
If you are having a problem with a particular account-- why not use one of the many available free web-based accounts
http://www.myway.com/
... if you abandon your current account for a while --they will lose interest-- then go back later on, maybe cancel that account (if it's with your ISP) and set up a new one-- with a new email address. There are forwarding services which could 'forward' your emails from the old address to the new one.
http://www.emailaddresses.com/email_forward.htm