How often do you check your physical mailbox? What's the worst outcome if you didn't read an email for 4 hours? So why do you have something interrupt you every 5 minutes to tell you about a new message? Notifications are distractions. 99% of people don't need them. You'll get more done and be happier if you focus on one thing at a time. So turn off the notifications and check email 2 or 3 times a day instead.
Got an hour to kill? Watch the Inbox Zero video. It'll teach you how to be better at email.