kmail is not sending my messages...

I'm trying to send messages via kmail(1.5.2) in my SuSE 8.2 distribution, it seeems everything works fine when I send a message, but the receiver is not getting anything. The intanet administrator told me that my messages are returning, but the kmail does not notify anything!!! There is a bug or am I forgeting some configuration parameter? (Before I was using the 1.4.3 vesion and I dd not ae this problem? Thanks in advance, Gustavo Adolfo