@SILdoc("The time in minutes before terminating and re-issuing the IDLE command, in order to keep alive the connection, by resetting the inactivity timeout of the server. A standards compliant server must have an inactivity timeout of at least 30 minutes. But it may happen that some IMAP servers don't respect that, or some intermediary network device has a shorter timeout. By setting this option the above problem can be worked around. This variable takes a number as a value. Default is 29 minutes. ")