It is a violation of the Twitter Rules to post the private and confidential information of others. For more information on this policy, please see the following policy page: http://support.twitter.com/entries/18368
That’s the message that Guy Adams got from Twitter support. But here’s the thing: there’s nothing on that page which says what Twitter support says it says. The closest that the rules come is this:
If someone requests you remove information that you posted about them, please respect their privacy and consider taking it down.
Unless Gary Zenkel asked Adams to take down the tweet and Adams refused — and there’s no indication that happened — it seems that Twitter is incapable of reading its own guidelines.
Update: I’ve now found these guidelines, which are a bit more on-point: they say that posting “non-public, personal email addresses” is a violation of the Twitter rules. Which, this email address (Gary.email@example.com) is both public and corporate.