Petition CCP and they will tell you "this is a known issue" and that they "are working on it".
Only 2 partial workarounds I know so that you can continue to see both mails and notifications while playing. It's clunky, but works:
- For e-mail, use EVE Gate, there is no way you will be able to see your mails from the the mail function ingame. So open up ingame browser and open your mail thru EVE Gate
- Notifications do work. When you log on and try to open mail, you will get the error message but the mail window will open. Change to the notifications tab and then minimize, do not close, the mail window.
You can now see any notifications. If you log off with notifications open, when you log back on notifications will be default when you open mail and you won't get error message (though you will still not be able to see the mails in the mail tab).
And let's hope CCP is quicker on this MAC fix than some others.
This also a "think twice warning" to any MAC user planning to do a clean reinstall for any reason. Don't, unless you want to live like this in EVE for a while.