seeing mails on macbook
I used to have tons of sync issues when attempting to use certain Exchange accounts with Mail.app and issues are still being reported with Yosemite: 

see this discussion - https://discussions.apple.com/message/26903397#26903397 

If you have to use a Microsoft account and you're running a mac, you might want to consider changing your mail client. The user above actually has gone back to using Outlook 2011 for compatibility.