Doctors may no longer make house calls, but they are answering patient e-mail messages - and being paid for it. In a move to improve efficiency and control costs, health plans and medical groups around the country are now beginning to pay doctors to reply by e-mail, just as they pay for office visits. While some computer-literate doctors have been using e-mail to communicate informally with patients for years, most have never been paid for that service. Brian Settlemoir, 39, an accountant in Folsom, Calif., recently sent an e-mail message to his doctor at the Creekside Medical Group to ask...