Blackberry uses their own server/service to relay email out, based on your email address, which could be treated as “spoof” in many email servers.
Afteroffice mail server reject these incoming email from Blackberry for the same reason too.
To disable spoof prevention system, you can:
By disabling the spoof prevention, users may get more spam carrying their own email address as the “Sender”.
However, to guarantee the incoming email from Blackberry will not be treated as spam, you'll need to perform the following: