You may be experiencing something I have come across, specifically in international communications where different alphabet setting are used in sender's and recipient's countries (even repeatedly with specific senders/recipients only even though same countries being involved for others where it never occurs). I have never found the precise reason or an exact explanation - however, I know of a solution that has worked in the past: Ask the sender to repeat the transmission in Plain Text, and do so by sending your message under the "Reply" button (not as a separate transmission) so your correspondent sees how you got the message. Remember to send in Plain Text yourself.