In such a case, the agency should notify the employee affected that such access was obtained when the employee returns. For purposes of national security. An agency which monitors e-mail should do so in the least intrusive way possible to acquire the required information. Usage statistics, for example, may only require the date and time stamps of messages, rather than the sender and recipients' names. System maintenance on a mailbox may only require gathering header information, rather than the entire contents of messages.
Similar considerations apply to access to e-mail by employer in employee's absence.
In all cases, it is important to notify individuals subject to monitoring in advance what the rules are. Employees should be notified when they are hired, or when they are given access to e-mail, of any monitoring programs in effect. In addition, they should be notified in advance before any new monitoring program. Business partners should be notified about monitoring when the partnership is established or in advance of any new monitoring program. Agencies should also conisder whether, and how, to notify any other correspondents of their employees.