AOL and emails with no content

[SecondSight]

Hello 

Since I upgraded to version 4, a few members who have AOL receive emails which have no content  except a message like this (I'm translating and it may not sound very English...) :

This message can't be shown because of it's format. Please ask the sender to send it again using another format or another software. multipart/alternative

I don't know AOL. Is there something which can be done ?

Thank you