From what we know of Jobs's personality, I sincerely doubt he'd allow anyone to write in his name. E-mails coming from Executive Relations would almost certain

From what we know of Jobs's personality, I sincerely doubt he'd allow anyone to write in his name. E-mails coming from Executive Relations would almost certainly be marked as coming from Executive Relations. He responds to very few e-mails sent to sjobs@apple, we just see almost all of the responses (it's highly probable that messages sent to him are pruned before he sees them). Plus, the responses almost always have iPhone as the X-Mailer, something that would be highly unlikely were they being written by some low-level PR employee sitting at a desk.