Slow in mac os x

I am using notes 9 on Mac OS X and have quite a large mail database. The problem I have is, everytime my notes client check for e-mail in the server, notes client and sametime embedded client froze. I cannot do anything. After it finished, then notes client starts to work again.

Does anybody have the same issue? If you do, any suggestion on how to fix it?

Thanks a lot in advance