Fatal Error after sending messages.

Hi, i'm new here. I'm a php developer and just today I decided to give Elgg a chance and i'm very happy with this cms, so powerful and flexible. So now I'm here because I got a problem when i send messages, after i send it I get a fatal error saying "CRLF injection detected" but the strange fact is that the messages still arrive without any problem to the other person, the problem doesn't appear when i reply to messagges but only when i send new ones to new users. What can I do to fix this? Is this a problem with my SMTP email? Thank's in advance.