Government e-mails and open government, revisited
If you recall, this is what got Sarah Palin in trouble back in 2008, when it was discovered she was using a Yahoo account for official business.
Also, public email accounts (and anything on a public computer, unless it's specifically protected by law) is public record. Not just elected officials, but public sector employees can have their email accounts subjected to a public records request.
It's simply an extension of paper records being public.
Recording phone conversations doesn't follow. We weren't recording phone conversations in 1950 or face-to-face conversations in 1850. No reason to do so now.