This may seem extreme, but it will help you focus without interruption. You might also turn on airplane mode or Do Not Disturb mode while you’re working. Schedule breaks throughout the day to check and respond to email, and resist the urge to check otherwise.
This also aligns with the Getting Things Done philosophy, for which @LeeAase is a trainer. When your brain is constantly switching tasks, you’re less productive than if you complete one task and then move on to the next.