Why am I not getting one person's emails?

This sounds stupid, I know. I'm getting all my work email just fine except my boss'! It used to work fine. But for example, this morning I had been answering my emails through my bb and then when I logged into Novell GroupWise (work email) I saw that my boss had sent two emails in the midst of all those others and they had never come through my bb. This has been happening for several days now. Any ideas? He has an iPhone if that's relevant at all. Any reason why this might be happening?

Thanks!