To help you stay focused, we think adjustments to some OSX preferences are a great option. (Create your own screenshots before making changes, if desired).
A. Customize OSX System Preferences for Notifications
1. Select System Preferences from the Apple menu and go to Notifications.
2. Decide on either Banner (come & go) or Alert (you dismiss) style notifications.
3. Think about turning off "Play sound for notifications", we like it that way.
B. Adjust OSX Mail Preferences
1. Open Mail Preferences to the General tab and try the following changes.
2. If possible, set to "Check for new messages" every 5 minutes. (This allows time for server-side mail processing to Sane folders).
3. See that "New message notifications" is set only for VIP's, (your priority contacts will still get the royal treatment, with the OSX Mail VIP feature in use).
C. Use a rule to make Mail Notifications more pertinent
1. Go to the Rules section of Mail Preferences.
2. Add a new rule, and give it a name in the "Description" field.
3. + Add: "Sender is in my contacts", "Sender is not in my previous recipients", "Sender is VIP".
4. Set "Perform the following actions", to Send Notification, OK, and Apply.
Using settings like these help keep your mail notifications limited to a more justifiable distraction level. These changes are a big help for us. We hope they are for you too.