I don't get to send e-mail for some servers

[kanchadales]

Hi,
I have a server with Merak 8.0.3 and pesk 7.5.6.

I am not getting to send e-mail of this server for some other servers, as, www.uol.com.br and www.terra.com.br
I believe to be problem related with the rDNS

But my Date Center, it already verified and the rDNS this ok.
Does anybody can me to help?