I used to be very diligent about responding to email, with the exception of complex or difficult communications where I needed time to think. At this point, I'm simply announcing what has already become de facto reality. I no longer respond to most email on the same day I receive it. I will also begin to triage my email more aggressively, which means far fewer courtesy responses, thank yous, and follow up notes than is my wont.
This is not me being ill socialized or rude. This is me acknowledging my time and cognitive constraints.
Please, feel free to write me if we have business, or are friends, or you are just so moved. But please do not be offended if you do not hear back from me promptly, or even slowly.
This is not how I would have it be, but this is how I must handle things.