In this situation, what an employer is worried about is FMLA "interference" - the idea that the employer is denying the employeee FMLA benefits to which he otherwise was entitled.
In summary, an employee is unlikely to establish an FMLA interference claim simply because he responds to some e-mail and a few phone calls during leave.
Generally, courts find that fielding occassional calls and e-mails that relate to your job while on leave is a "professional Courtesy" that does not interfere with FMLA leave. Therefore, a few work related communications likely will not constitute interference with an employees FMLA rights As one federal court in New York put it, when an employee is passing on "institutional knowledg" or providing closure on open assignments , employers do not violate the FMLA.
