I don't think that it is sufficient for the email deferring to only happen on the client side. There should be a way to have mail hit a holding area in your inbox and only appear again during office hours. I'm not sure if any mail server software implements something like this.
Gmail for friends + private stuff (work seeking etc)
Work email for das work stuffz.
Works well. Only one email account to ignore after-hours and over weekends.
Plus - if you use your private email for work, they may have the mandate to look at your private email as it was done on company property using company equipment (ADSL and line rental included). Not worth the hassle and stress.
So the stress will only be tenfold the next morning, and you will spend half your day sifting through emails and some people forgetting what the issue was from the previous day and just create a snowball effect?
Maybe get "Banning sales emails/calls after 5" right first before trying to implement banning work emails completely.