problems with SMTP and encryption

I am having difficulty sending email.
My application encrypts a load of data using Visual Soft Crypt (IDEA encryption algorthym) which it then inserts into the body of an email. The email is sent using IP*Works 4 SMTP component.

This works fine and the correct text is definatly inserted into the email. However when the email is recieved half the body of the email is missing.

I wonder if there are any weird characters in the encrypted digest that the email system is having difficulty with.

Any Ideas or Solutions?

Alex